A compound from the RNiO₃ family of strongly correlated oxides, NdNiO₃ (NNO) exhibits temperature driven metal to insulator (MI) and magnetic transition (paramagnetic to antiferromagnetic one). To understand the role of magnetism on electronic structure of NNO we performed temperature dependent high-resolution angle-resolved photoemission spectroscopy (ARPES) study on perturbed electronic/magnetic structure of the ultra-thin film of NNO.
ARPES is a very surface sensitive technique which potential we fully utilized in combination with PLD. This approach gives us satiated control of the measured system. By using pulsed laser deposition (PLD), a bilayer systems consisting of underlying magnetically ordered film of La_1-xSr_xMnO₃ (and La_1-xCa_xMnO₃) and ultrathin film of NNO (2-5 u.c.) was created. By changing the content of Sr(Ca) we control magnetic ordering in the manganite layer from ferromagnetic metallic (x=0.33 , FM/M) to antiferromagnetic charged ordered one (x=0.66, AF/I). We have performed high#8208;resolution ARPES to map the electronic structure NdNiO3 films in 3D k#8208;space as a function of the temperature.
Obtained study gives important information about the influence of magnetic orders on the electronic structure and correlation effects in nickelates, with the potential to have a big impact on the field.

Current Li-ion batteries, which have been the primary focus for electrical energy storage development in the past 40 years, are approaching their theoretical limits. Divalent Mg-ion battery technology, with potential high energy density and volumetric capacity, may provide alternative solutions to meet the fast-growing global demand for energy storage. The prototype Mg-ion battery system was established almost 15 years ago [D. Aurbach et al. Nature 407, 724 (2000)], where a complex organohaloaluminate/tetrahydrofuran (Mg(AlCl₂BuEt)₂/THF) solution is developed as the electrolyte that is sandwiched by a Mg metal (anode) and a Mo₆S₈ (cathode) to form the electrochemical cell. Despite the remarkable success of this prototype system, we still lack a clear understanding of the fundamental Mg intercalation/deposition mechanism at the electrolyte/electrode interfaces that perhaps results in the observed sluggish Mg transport process.
Our previous work has shown that the Mg-ion is strongly coordinated in the bulk electrolyte by a combination of counterion, Cl^-, and organic aprotic solvent, THF. The solvation energy can easily exceed 2 eV due to the strong electrostatic interactions between Mg²⁺ and its ligands. [Wan and Prendergast, JACS 136, 14456 (2014)] With this information, one can imagine the difficulties to strip all its ligands away at the interface and allow Mg²⁺ to intercalate/deposit into the bulk electrolyte. In this work, we focus on the Mg²⁺ intercalation process at the Mo₆S₈ cathode surface. The solvent-surface interactions are first studied using density functional theory. With the presence of positively charged MgCl⁺ unit on the surface, a change of THF binding energy to the surface is observed. Upon Mg intercalation, the counterion Cl^- is striped away from the surface and the dissociation energy between Mg²⁺ and Cl^- is approximated using the nudged elastic band method. Finally, a complete Mg intercalation mechanism is proposed and the unique role of Mo₆S₈ as the cathode material is emphasized.
This work is supported as part of the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.

All-solid-state batteries have the potential to dramatically improve the capacity and safety of high-density energy storage. Inorganic electrolytes with sufficiently high conductivity and mechanical and thermal stability are needed to develop these batteries. Understanding the effect of the electronic structure on Li conductivity will provide design rules to improve promising materials accelerate high-throughput screening of potential electrolytes. Using a recently synthesized highly conductive electrolyte candidate, Li₃InBr₆, and other superionic electrolytes, we characterize the effect of the local electronic structure on Li diffusivity using first-principles molecular dynamics simulations. The insights gained from our in-depth characterization of the Li transport mechanism in this promising material will aid the search for better inorganic solid-state batteries.
This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

The knowledge of the electronic structure is fundamental to the understanding of material properties, and therefore to the discovery and optimization of energy materials. Resonant inelastic x-ray scattering (RIXS) combines the potential of x-ray emission and x-ray absorption spectroscopies, simultaneously probing the occupied and unoccupied electronic structure in an element and orbital-specific fashion. A photon-in photon-out technique, RIXS has been applied to a growing range of in-situ and constrained sample environments since its inception in the mid-90s. Concurrently, the technique has also benefited from drastic improvements in energy resolution, reaching a level where simultaneous measurements of low-energy electronic, magnetic and structural excitations are now possible. I will report on a few recent applications of RIXS related to the study of superconductivity in 3d and 4f electron systems, and catalysis in 5d electron materials. Through these studies, I will show that RIXS is a powerful tool well suited for exploratory tasks in energy science, such as discovery of new superconductors and design or optimization of catalysts. I will also touch on the future of RIXS, as further improvements in energy resolution are soon expected with the current development of new instruments such as the SIX beamline at NSLS-II.

Advanced energy technology arises from the understanding in basic science, thus rest in large on in-situ/operando characterization tools for observing the physical and chemical interfacial processes in energy materials and devices, which has been largely limited in a framework of thermodynamic and kinetic concepts or atomic and nanoscale. In many important energy systems such as energy conversion, energy storage and catalysis, advanced materials and functionality in devices are based on the complexity of material architecture, chemistry and interactions among constituents within. To understand and thus ultimately control the energy conversion and energy storage applications calls for in-situ/operando characterization tools. We have developed the in-situ/operando soft X-ray spectroscopy for the studies of catalytic and electrochemical reactions in recent years, and overcome the challenge that soft X-rays cannot easily peek into the high-pressure catalytic cells or liquid electrochemical cells. The unique design of in-situ/operando soft X-ray spectroscopy instrumentation design and fabrication principle and a number of examples will be presented, including the nanocatalysts and the recent experiment performed for studying the hole generation in a specifically designed photoelectrochemical cell under operando conditions.

Tuning the carrier density in transition metal oxides provides the opportunity to controllably access the various electronic phases such as metallic, insulating, and superconducting, commonly found in these materials. Recently, ionic liquid gated electric double-layer transistor (EDLT) structure has attracted much attention as an effective technique to modulate the carrier density beyond the typically accessible range by solid-state gating techniques [1-4]. Under such high carrier densities, a strong electronic structure modification is expected to occur locally at the oxide/ionic liquid interface. However, the understanding of the oxide/ionic liquid interface and the oxide electronic structure under ionic liquid gating conditions has been limited.
Here, we present a comprehensive study of electrical transport and in-situ X-ray absorption spectroscopy (XAS) in ionic liquid/gel gated ultra-thin La_0.7Sr_0.3MnO₃ (LSMO) films to better understand the charge modulation effect by ionic liquid/gel gating. LSMO is a well known ferromagnetic metal in bulk at room temperature which has recently been reported to exhibit metal-insulator transition as the thickness is reduced [5-7]. The ultra-thin LSMO films prepared by pulsed laser deposition on SrTiO₃ (001) substrates were coated with ionic liquid and a gate electrode to form the EDLT structure. By applying a negative bias to the gate electrode, a metallic state was stabilized which could be switched to an insulating state reversibly by applying a positive bias. To explore the origin of this phenomena, we employed in-situ XAS technique on these devices to probe the manganese valence state during the application of gate voltage. The Mn-L_2,3 edge spectra showed features characteristic of valence change under application of bias which will be discussed in relation to the transport data.
[Reference]
[1] K. Ueno, et al., Nat. Mater. 7, 855 (2008).
[2] H. T. Yuan, et al., Adv. Funct. Mater. 19, 1046 (2009).
[3] M. Nakano et al., Nature 487, 459 (2012).
[4] J. Jeong, et al., Science 339, 1042 (2013).
[5] B. Kim, et al., Appl. Phys. Lett. 99, 092513 (2011).
[6] B. Kim, et al., Sol. Stat. Commun. 105, 598 (2010).
[7] M. Huijben, et al., Phys. Rev. B 78, 094413 (2008).

Most of the electrochemistry processes occur within the thin layer of electrolyte at the electrolyte / electrode interfaces, commonly denoted as the electrical double layer (EDL). In spite of some classic EDL theories, very limited experimental information is available about these solvent or solute species within such EDLs. We have developed in-situ liquid cells to study such electrolyte / electrode interfaces by means of soft x-ray absorption spectroscopy. [1] With this in-situ and operando XAS technique, we characterized the interface between gold / platinum electrode and water or sulfuric acid solution. It was found that the interfacial water layer has significantly different hydrogen-bonding network structure compared to the bulk water. Under different bias, the polar water molecules will respond to the external electrical field and reorient at the gold electrode surface, which significantly changes the amount of distorted or broken hydrogen bonds. [1] We were also able to identify some intermediate surface species during Pt-catalyzed OER reaction under working conditions.
[1]. J. J. Velasco-Velez, C. H. Wu, et al., Science, ASAP.

The safety issue of LIB has been considered as a one of the most crucial drawbacks that must be improved for the application of power sources of plug-in hybrid electric vehicles (PHEVs) and electrical vehicles (EV). One of the main reason that might cause safety hazards of the LIB cell is associated with the thermal instability of cathode materials, especially at their charged states. Reportedly, charged cathodes are unstable at high temperatures and exothermically decomposed with liberating oxygen. The released reactive oxygen may lead to an increased inner cell pressure and violent reactions with electrolytes heated above its flash point. Therefore, in-depth understanding of the thermal decomposition behavior with oxygen release and their relationship to the thermal stability of the charged cathode material is very important.
In this regard, we have developed techniques using a combination of the in situ time-resolved X-ray diffraction (TR-XRD) and mass spectroscopy (MS) to monitor the structural changes and gas evolution during the thermal decomposition of charged cathode materials. In addition, in situ X-ray absorption spectroscopy (XAS) during heating has been also developed to look at the local and electronic structural changes occurring during thermal decomposition in an elemental selective way. By employing these combined in situ techniques, we are able to understand various aspects of the structural and electronic structure changes in the charged cathode materials during thermal decomposition; these include thermal decomposition paths, differences in phase-distribution, phase nucleation and propagation, the preferred atomic sites and migration paths of transition metal cations (Ni, Co, Mn, and Fe) and their individual contributions to thermal stability, together with measuring the oxygen release that accompanies these structural changes during heating. In this talk, several case studies on various cathode materials including layer-structured LiNi_xMn_yCo_zO₂ and high-voltage spinel LiNi_0.5Mn_1.5O₄ will be covered. These results will provide valuable guidance for developing new cathode materials with improved safety characteristics.
ACKNOWLEDGMENT
The work done at Brookhaven National Lab. was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. DOE under Contract No. DE-AC02-98CH10886. K. N. was supported by the Dongguk University Research Fund of 2014.

The heterogeneous chemistry of solid/vapor, solid/liquid, and liquid/vapor interfaces governs many processes in catalysis, electrochemistry, and the environment. Examples include the removal of harmful components from automotive exhaust streams, heterogeneous reactions at the electrodes of solid oxide fuel cells, cloud droplet nucleation on atmospheric aerosols particles, as well as the uptake and release of trace gases by the polar snowpack. The prospects for a fundamental understanding of the basic reaction mechanisms at these interfaces on the molecular scale and under realistic operating conditions have greatly improved over the past decades through the development of in situ surface science methods, among them ambient pressure photoelectron and near edge X-ray absorption spectroscopy. This talk will discuss the application of these techniques to studies of the reaction of water vapor with oxide surfaces as well as new strategies for measuring liquid/solid interfaces by means of photoelectron spectroscopy.

Metal Organic Frameworks have emerged in applications related to gas separation and storage, sensing, and optoelectronic devices. In this work, HKUST-1 (also known as Cu₂(BTC)₃, BTC=1,3,5-Benzenetricarboxylate) MOF thin films are interrogated for co-adsorption of gases using Ambient Pressure Photoemission Spectroscopy (APPES) at the Advanced Light Source. The competitive adsorption between water and nitric oxide or water and ammonia are examined. APPES provides information about changes in metal center oxidation state, the bonding configuration of adsorbate, and binding strengths. Changes in the metal center oxidation state lead to differences in adsorption behavior. We find that NO adsorbs more strongly to photo-reduced Cu¹⁺ as compared to Cu²⁺ in the presence of water. This highlights the potential of MOFs with lower oxidation state metal centers for selective adsorption of gases in the presence of water.[1] Degradation of HKUST-1 in the presence of water and results from the bonding of ammonia to the unsaturated metal center that weakens the copper-ligand bond. This weakened copper-ligand bond enables water to replace the ligand, ultimately degrading the MOF.
[1] Nijem et. al. Chem. Comm., 2014, 50 (70), 10144 - 10147

Fossil-fuel power plants are among the largest CO₂ emission sources accounting for approximately one-third of anthropogenic CO₂ emission. Due to increasing energy demands and slow deployment of clean energy alternatives, a practical near term route to CO₂ mitigation is through CO₂ capture and utilization. Currently, CO₂ capture from power plants is typically done using aqueous solutions of monoethanolamine (MEA). We have used in-situ X-ray spectroscopic methods including ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and resonant inelastic X-ray scattering (RIXS) to monitor CO₂ uptake by thirty weight percent aqueous solutions of MEA, a standard concentration used in industry. Disadvantages of using aqueous MEA solutions include: high costs for regenerating the MEA solution after CO₂ capture, solution degradation by flue gases like NO_x and SO_x, and equipment corrosion by the MEA solution. As a result, solid supported capture materials are being investigated as alternatives to aqueous MEA solutions for CO₂ capture. We have used a model system approach to provide a molecular-level understanding of solid supported CO₂ capture materials. We studied the adsorption of MEA on rutile TiO₂(100) surfaces with complementary surface science methods, including synchrotron based X-ray photoelectron spectroscopy (XPS), Near Edge X-ray Adsorption Fine Structure (NEXAFS) and Scanning Tunneling Microscopy (STM), and Density Functional Theory (DFT) calculations and investigated its potential for CO₂ capture with AP- XPS. By correlating this system&’s CO₂ capture capabilities with an understanding of the bonding of MEA to the TiO₂(110) surface a structure-property relationship was established. This allowed the development of an improved model solid-supported CO₂ capture material based on monopropanol amine (MPA) adsorbed on TiO₂(110).

Ag₂VO₂PO₄ presents an interesting material to validate recent design principles for developing higher energy density lithium ion battery (LIB) cathodes without compromising safety. In particular, the combination of multiple readily accessible vanadium charge states (V⁵⁺, V⁴⁺, V³⁺), chemically stable PO₄^3- groups, and the formation of a conductive Ag⁰ network during the lithium insertion are considered to be responsible for Li/Ag₂VO₂PO₄ batteries demonstrating 205 mA h g^-1 to 2.0 V and 270 mA h g^-1 to 1.5 V. Detailed understanding of the reactions occurring in this system requires the use of computational studies, such as density functional theory (DFT) based electronic structure calculations and molecular dynamics (MD) simulations. The experimental knowledge regarding the evolution of the Ag and V coordination environments during the lithiation needs to be augmented to critically examine the results from DFT and MD. The use of traditional x-ray diffraction techniques to study the structural and chemical environment is not suitable for studying Li/Ag₂VO₂PO₄ because of the loss of sharp Bragg peaks during the electrochemical discharge process. Instead, local probes of the evolution of the structural and chemical environments are required that do not rely upon long-range order. Here, we present our results combining in-situ pairs distribution function (PDF) measurements with ex-situ soft x-ray photoelectron spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) of carefully disassembled cells. The in-situ PDF monitored the evolution of the local structure, whilst ex-situ XPS and V L_3,2-edge NEXAFS tracked the reduction of the Ag and V ions. We will compare our experimental findings to results from DFT and MD computations. This research was funded by a Network of Excellence grant from the Research Foundation of the State University of New York.

Yanwu Xie,^1,2 Sarp Kaya,^3,4 Hirohito Ogasawara,^3,4 Makoto Minohara,² Yasuyuki Hikita,² Christopher Bell,² Anders Nilsson,^3,4 Harold. Y. Hwang^1,2
1Geballe Laboratory for Advanced Materials, Department of Applied Physics, Stanford University, Stanford, California 94305, USA
²Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
³SUNCAT Center for Interface Science and Catalysis, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
⁴Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
An important concept in designing oxide electronics is creating functional interfaces. A good example is the LaAlO₃/SrTiO₃ (100) heterostructure, which is known for its emergent conducting interface between the two band insulators [1]. From an ionic viewpoint, along the (100) direction, LaAlO₃ can be viewed as alternate stacking of positive (La³⁺O^2-)¹⁺ and negative (Al³⁺O₂^4-)^1- atomic layers, and thus the heterostructure has a polar LaAlO₃ surface [2]. Since polar oxides are extremely susceptible to ambient water vapor, it is of fundamental interest to understand how their surfaces interact with water and consequently affect proximate functional interfaces. In a recent experimental study [3] we have shown that the electronic conductivity at the LaAlO₃/SrTiO₃ interface can be strongly modulated by the exposure to water. However, a microscopic understanding of the change was lacking. In this work, using ambient pressure synchrotron X-ray photoemission spectroscopy, we studied the adsorption of water at the surface of the LaAlO₃ /SrTiO₃ (100) heterostructure. The samples were prepared by depositing LaAlO₃ thin film on SrTiO₃ (100) single-crystal substrate using pulsed laser deposition technique. Our results show that, upon increasing the water vapor pressure P from ultra-high vacuum to 1 Torr, water firstly adsorbs dissociatively at surface defects of the AlO₂-terminated LaAlO₃ (001) surface ( P < 10^-4 Torr), and then dissociates at surface Al atoms until saturation with a monolayer of hydroxyl (10^-4 Torr < P < 5×10^-2 Torr), while the molecular water is largely adsorbed on top of the hydroxyl groups. The hydroxylation of the LaAlO₃ (001) surface leads to a downward band bending up to 0.7 eV across the LaAlO₃ film, suggesting an electron transfer from the surface to the interface.
This work is supported by the Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-76SF00515. Y.X. also acknowledges partial funding from the AFOSR-MURI on “Quantum Preservation, Simulation & Transfer in Oxide Nanostructures”.
[1] A. Ohtomo & H. Y. Hwang, Nature427, 423 (2004).
[2] N. Nakagawa et al., Nat. Mater.5, 204 (2006).
[3] Y. Xie et al., Nat. Commun. 2, 494 (2011).

The traditional approach to the optimization of metal/oxide catalysts has focused on the properties of the metal phase. A low concentration of chemically active sites in the oxide support may be blocked by the anchoring of metal nanoparticles. By using a second oxide as a support (host), one can create a multifunctional con#64257;guration in which both metal and oxide nanoparticles are exposed to the reactants [1]. As an example, depositing ceria on TiO₂(110) leads to the formation of ceria dimmers [1]. Atoms with properties ranging from metallic to ionic are available at the metal-oxide interface and create unique reaction sites. We show the creation of an efficient pathway for the water-gas shift reaction at the oxide-metal interface of ceria nanoparticles deposited on Cu(111) or Au(111). In situ experiments demonstrated that a carboxy species formed at the interface is the critical intermediate in the reaction [2]. Our studies point to a new paradigm in the design of catalysts: The optimization of the oxide phase and the metal-oxide interface in a catalyst can improve substantially its activity and selectivity. Using this knowledge, we show have to create a new multifunctional active site for the conversion of CO₂ to methanol.[3]
[1] Chem. Rev 113, 4373-4390 (2013)
[2] Angew. Chem. Int. Ed. 52, 5101-5105 (2013)
[3] Science, 345, 546-550 (2014)

Super-protonic conductivity is a highly-wished-for functionality of solid electrolytes for intermediate temperature ceramic fuel cells and steam electrolyzers. Yttrium-substituted barium cerate and barium zirconate (BZY, BCY) - conventional ABO₃-type ceramics with perovskite structure, are well-studied candidates for this purpose.
We have investigated the functional oxygen vacancy filling of engineered oxygen deficient BCY/BZY by water molecules with electro-analytical methods and ambient pressure XPS [1], which enabled to sketch a detailed picture of the correlation of molecular and electronic structure changes, and the concomitant onset of proton conductivity at elevated temperatures.
With this information we were able to design experiments, where the proton phonon coupling could be quantitatively investigated with high pressure-high temperature electrochemical impedance spectroscopy combined with quasi-elastic neutron scattering [2,3]. Supported with pressure dependent XRD and Raman scattering data [4,5] we were able to correlate the proton jumping parameters with the temperature and found that the proton jump times follow a Holstein polaron relation [6-9].
[1] Q. Chen et al., Chem. Mater. 25 (23), 4690 (2013).
[2] Q. Chen et al., Solid State Ionics 252, 2 (2013).
[3] Q. Chen et al., High Pressure Research 32(4), 471 (2012).
[4] Q. Chen et al., J. Phys. Chem. C 115 (48), 24021 (2011).
[5] Q. Chen et al., J. Eur. Ceram. Soc. 31 (14), 2657 (2011).
[6] Q. Chen et al., Appl. Phys. Lett. 97, 041902 (2010)
[7] A. Braun et al., Appl. Phys. Lett., 95, 224103 (2009).
[8] Q. Chen, Effects of Pressure on the Proton-Phonon Coupling in Metal Oxides with
Perovskite Structure, Diss., Eidgenössische Technische Hochschule ETH Zürich, Nr. 20554, 2012
[9] A. Braun, Q. Chen, Experimental evidence for the proton polaron in
metal oxide hydrates, submitted for publication.

Materials have traditionally been introduced into technology either by incremental improvements on long-known substances (Si, CIS, CdTe, In2O3) or via chemical substitution of known materials or by serendipity. This time-honored tradition leaves out the possibility of yet undiscovered but potentially useful materials. Inspection of databases of all inorganic materials previously made (ICSD or ICDD) reveals that a few thousands are simply missing. These are combinations of chemical elements that are analogous to those appearing listed compounds but represent unreported compounds. One wonders if they are missing for a good reason (such as some inherent instability), or the community has simply not gotten around to try and make them, yet they might be interesting. Systematic laboratory synthesis of all such candidate-missing materials would seem a horrendous project. A possible alternative is to perform initial screening of hundreds of Missing Compounds by using first-principles thermodynamics, and then attempt laboratory realization of narrower lists of missing materials. I will describe in this talk the basic idea behind First Principles Quantum Thermodynamics leading to the prediction of scores of previously missed A2BX4 chalcogenides as well as ABX 1:1:1 compounds such as the 18 electron III-X-V ;II-X-VI; IV-X-IV; V-IX-IV; and IV-IX-V groups. Synthesis efforts by three synthesis teams —the Northwestern Mason group, and Poeppelmeir group, the OSU Keszler group -will be described.

The development of electron and scanning probe microscopies in the second half of XX century have produced spectacular images of internal structure and composition of matter with nanometer and now atomic resolution. Much of this progress since 80ies was enabled by computer-assisted methods for data acquisition and analysis that provided automated analogs of classical storage methods. However, the progress in imaging technologies since the beginning of XXI century has opened the veritable floodgates of high-veracity information on atomic positions and functionality, often in the form of multidimensional data sets containing partial or full information on atomic positions, functionalities, etc. In this presentation, I will discuss several examples of high-resolution studies of the structural, electronic and electrochemical properties of oxide surfaces enabled by multidimensional scanning probe microscopies synergistically combined with the big data technologies. On the mesoscopic scale, combination of strain- and current sensitive scanning probe microscopies allows to build nanometer-scale maps of local reversible and irreversible electrochemical activities. The use of multivariate statistical methods allows separating the complex multidimensional data sets into statistically significant components which in certain cases can be mapped onto individual physical mechanisms. I will further discuss the use of in-situ Pulsed Laser Deposition growth combined with atomic resolution Scanning Tunneling Microscopy and Spectroscopy to explore surface structures and electrochemical reactivity of oxides on the atomic scale. For SrRuO₃, we directly observe multiple surface reconstructions and link these to the metal-insulator transitions as ascertained by UPS methods. On La_xCa_1-xMnO₃, we demonstrate strong termination dependence of electronic properties and presence of disordered oxygen ad-atoms. The growth dynamics and surface terminations of these films are discussed, along with single-atom electrochemistry experiments performed by STM. Finally, I explore the opportunities for atomically-resolved imaging and property data mining of functional oxides extending beyond classical order parameter descriptions, and giving rise to the deep data analysis in materials research.
This research is supported by the by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division, and was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, BES DOE.

In this presentation I will make a short review of the basic ideas behind electronic structure theory, leading both to the ‘conventional&’ description of essentially non-correlated electronic structures, as well as to correlated electron systems where dynamical mean field theory is an important recently developed tool. Examples of how these theories perform in reproducing materials will be primarily given from the group of magnetic compounds, where recent energy relevant applications concern e.g. magnetocalorics and rare-earth free permanent magnets. Special attention will be given to the dynamics of magnetic materials, using an atomistic spin-dynamics method that is coupled to electronic structure theory via a multi-scale approach.

Rechargeable Li-ion batteries (LIB) are a promising technology for efficient energy storage. We have carried out critical in operando neutron measurements on Li distribution and transport to gain new insights in the function and failure of battery systems. Four neutron measurement techniques, neutron depth profiling (NDP), neutron reflectivity (NR), small angle neutron scattering (SANS), and neutron imaging (NI) have been used to quantify real-time information of the Li transport in electrode, sub-nanometer thin film and interfacial structures, and fracturing of electrode particles. NDP data show that a true measure of the Coulombic efficiency requires the quantification of both ionic and electric charge displacements in a single trip and the discrepancy between the ionic and electric transport is a powerful indicator of the onset of battery failure. Tomographic 3D NDP helps map lithium distribution in electrodes to indicate spatial heterogeneities of lithium in cathodes that had undergone different electrochemical cycling histories. NR probes depth-dependent compositions and interfacial structures in buried thin films with sub-nanometer resolution and correlates the lithiation state with the integrity of electrode films. Using a thin amouphouse silicon film having undergone lithiation and delithiation cycles, in operando NR reveals that a “pore collapse and regrowth” mechanism is responsible for highly reversible cycling of the nanoscale slicon anode. Quantitative analysis of in-situ SANS data yields the total area of fracture surfaces of graphite particles induced by lithiation/delithiation cycling. The information could be used to relate the capacity decay to the usable cycle life of LIBs. Real-time NI monitoring of the lithiation of highly-oriented pyrolitic graphite illustrates the existence of hot-spots near the surface, through which Li ions enter to intercalate the bulk of the graphite electrode. The findings demonstrate that in situ neutron measurements offer promising new opportunities for better understanding of rechargeable batteries.

The study of energy materials forms a significant proportion of the research carried out on the ISIS pulsed neutron spallation source, part of the Rutherford Appleton Laboratory campus, the UK&’s largest national laboratory. In order to study the functional properties of interest we often must commission new sample environment apparatus so that these properties may be investigated simultaneously with material structure or molecular dynamics. Furthermore, these apparatuses commonly must be able to operate at elevated temperatures and pressures, under gas flow or in vacuum and work with corrosive, air-sensitive or toxic chemicals. Experiments that comprise simultaneous, multi-technique characterisation in functionally significant conditions are termed ‘in-operando&’, and here I describe the development of 3 such systems.
A microwave resonator for simultaneous dielectric, structural and mass spectroscopy characterisation of solids during ammonia gas uptake at room temperature.
Simultaneous ionic conductivity and structural characterisation at high temperature under hydrogen atmospheres.
In-operando decomposition of ammonia gas over Li₂NH catalysis at high temperature and under gas flow.
This presentation will include details of apparatus design and commissioning, together with recent in-operando experimental results from all three systems. The insights gained from the in-operando experimental methodology will be highlighted.

In-situ techniques proved to be exceptionally useful tools to understand electrode materials for Li-ion batteries. Despite the great interest generated by neutrons&’ sensitivity to lithium, in-situ neutron diffraction (ND) knew a slow development due to the intrinsic difficulties it held. We recently designed an electrochemical cell manufactured with a completely neutron-transparent (Ti,Zr) alloy. Used with deuterated electrolytes, the cell is able to combine good electrochemical properties and the ability to collect ND patterns operando, with good statistics and no other Bragg peaks than those of the electrode material of interest. Importantly, this allows detailed structural determinations by Rietveld refinement during operation. The cell was validated using well-known battery materials such as LiFePO₄ (1) demonstrating real operando experiments conducted on the D20 high flux neutron powder diffractometer at ILL Grenoble,France. The cell was then used to study challenging materials. We report in particular on a series of spinel materials Li_1+xMn_2-xO₄ (x=0, 0.05, 0.1). The well-known difference in electrochemical performances (capacity fading) observed in this family of materials was thoroughly investigated using operando neutron diffraction. We synthesized LiMn₂O₄, Li_1.05Mn_1.95O₄ and Li_1.10Mn_1.90O₄ and observed their charging process in real time. The study (2) showed that not only the volume change induced by the delithiation is reduced while going from LiMn₂O₄ to Li_1.10Mn_1.90O₄, but more importantly that the mechanism by which this happens is modified. In fact, while Li_1.10Mn_1.90O₄ reacts though a "simple" monophasic reaction (a solid solution), Li_1.05Mn_1.95O₄ shows the existence of a solid solution process followed by a biphasic reaction and LiMn₂O₄ even shows a sequence of two biphasic reactions. Both the above mentioned features contribute to make overlithiated Li_1.10Mn_1.90O₄ a much better candidate for use in Li-ion batteries than the standard stoichiometric LiMn₂O₄. In more details, neutrons allow us to be sensitive to lithium&’s atomic parameters, such as atomic coordinates and even site occupancy factors (SOFs), and thus to include them in our Rietveld analysis to increase the accuracy of our time-dependent structural model. In the specific case of Li_1+xMn_2-xO₄ spinels this meant the possibility to correlate, for the first time, the evolution of lithium&’s SOF with the electrochemical features of the materials, which is of key importance for understanding and therefore improving Li-ion battery materials. Moreover, the cell will be used for several in-situ experiments in late 2014 (Mn and (Mn,Ni) spinels (dis)charge), not only using standard neutron diffraction, but also to develop in-situ Neutron Pair Distribution Function analysis. The first results of these experiments will be reported. Ref: (1) M. Bianchini et al., J. Electrochem. Soc., 160 (2013), A2176. (2) M. Bianchini et al., J. Phys. Chem. C (2014) accepted, DOI:10.1021/jp509027g.

In-situ Small-angle neutron scattering (SANS) was used to study adsorption of carbon dioxide (CO₂) in the porous carbon. The pore size distribution of the studied carbon is bimodal, with the average size of the mesopores and nanopores ~ 20 Å and 5 Å, respectively. The adsorption behavior of CO₂ in both meso- and nanopores was probed by measuring SANS intensity from CO₂-saturated sample as a function of relative pressure P/P₀ in the range of 0.0 to 0.85 at temperature T= 23^oC. The density of the confined CO₂ was estimated by analyzing Porod invariant at different P/P₀. Significant densification of CO₂ was observed in the nanopores, in which the density of the adsorbed fluid (ρ_CO2 ~ 1 g/cc) exceeded by a factor of ~ 15 the density of bulk CO₂ at the same pressure and temperature. The fluid densification in the mesopores is negligibly small as compared to densification in the nanopores. The CO₂ mass uptake at different pressures measured by SANS agrees with independent gas adsorption experiments. The pore size distribution of nanopores is pressure dependent: the average size of the pore increases initially with pressure and then starts decreasing at pressure P/P₀=0.25. In order to delineate the effect of hydrostatic pressure on the pore deformation, SANS experiments have been carried out using non-adsorbing fluid (Argon). It was found that SANS profiles remain unchanged with pressure indicating that the pore structure is not affected by the hydrostatic pressure. We tentatively assign the observed deformation of the nanopore to the strong interaction potential between pore wall and CO₂ molecules.

Hydrogen isotopes must be purified in nuclear energy applications, either to minimize environmental release of tritium from fission reactors, to reduce ¹H contamination in heavy water reactors, or to prepare appropriate gas mixtures for nuclear fusion experiments.[1] An especially effective category of isotope separation methods uses the strong isotopic dependence of the equilibrium between gas-phase hydrogen and condensed-phase hydrogen compounds. Palladium is a notable sorbent material for this purpose because it can reversibly form hydrides at near-ambient temperatures and pressures.[2] To design an effective separation system, the behavior of the sorbent material should be well understood.
One way to evaluate the isotope separation performance of a solid hydride is through a configuration similar to gas chromatography. In this experiment, a sorbent material is packed into a tube, and loaded with a given hydrogen isotope. Another isotope is then introduced at one end of the tube, and the outlet gas composition is monitored at the other end by mass or Raman spectrometry.[3] Under certain operating conditions, the chemical rate constants for the exchange of isotopes between the gas and solid phase can be derived. To improve confidence that these operating conditions are actually present, we have performed neutron imaging experiments that allow us to observe the location of ¹H throughout the column during an entire experiment, from when it first enters until it passes all the way through. The experiments reveal how a hydrogen-deuterium boundary responds to suboptimal flow conditions and to defects in a column, and also how the boundary evolves when more desirable conditions are restored. Our results have provided important insights into the interpretation of isotope exchange chromatography experiments that will aid future development of this category of separation technologies.
This work was supported by the Laboratory-Directed Research and Development program at Sandia National Laboratories, a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. The work was also supported by the U.S. Department of Commerce, the NIST Radiation and Physics Division, the Director's office of NIST, the NIST Center for Neutron Research, and the Department of Energy interagency agreement No. DE_AI01-01EE50660. SAND2014-18899 A
[1] Vasaru, G. Tritium Isotope Separation. CRC Press, 1993.
[2] Heung, L. K.; Sessions, H. T.; Poore, A. S.; Jacobs, W. D.; Williams, C. S. “Next-generation TCAP hydrogen isotope separation process.” Fusion Sci. Tech. 54 (2) 399-402, 2008.
[3] Foltz, G.W.; Melius, C.F. Studies of Isotopic Exchange Between Gaseous Hydrogen and Palladium Hydride Powder, J. Catalysis 108 409-425 (1987)

The proton conductor yttrium-doped barium zirconate, BaZr_1-xY_xO_3-δ (BZYx), has emerged as a promising material to be applied as an electrolyte in intermediate temperature (400 - 700 ^oC) solid oxide fuel cells (IT-SOFCs). The special interest on this material is due to its relatively high proton conductivity and chemical stability in CO₂ containing atmospheres. Therefore, the BZYx defect chemistry and the hydration characteristics must be fully characterized and understood prior to using this material in electrochemical devices. In the present work, the BZYx (x = 10, 20 and 30 mol% Y) hydration behavior was investigated for the first time using water adsorption calorimetry technique. A surface area analyzer with water vapor dosing system coupled with a Calvet-type microcalorimeter is used. Such system configuration allows precise dosing of water and in-situ measurement of adsorption enthalpies (ΔH_ads) using a relatively small amount of sample [1]. The experiment was performed from 25 to 600 ^oC aiming to obtain the enthalpy of bulk hydration (oxygen vacancies filling) as a function of dopant content and temperature. The BZYx powders were synthesized by the oxidant-peroxo method and heat treated at 1200 ^oC for 24 h [2]. The samples were characterized by electron microprobe, X-ray diffraction, thermogravimetry, infrared spectroscopy and surface area (BET) analyses. The water adsorption experiment was programmed in an incremental dose mode to provide 10 mu;mol of H₂O up to the equilibration pressure (~ 0.021 atm). The quantity of adsorbed water is higher when the content of dopant increases in the BZYx solid solutions from x= 0.1 to 0.3. The enthalpies of adsorption are found to be exothermic for all compositions and reach more exothermic values when the dopant increases from x = 0.1 to 0.2. From x = 0.2 to 0.3 there is only a small exothermic increment to the enthalpy of adsorption at 300 and 400 ^oC. The results indicate that defect clustering and defect association (Y partitioning among A and B sites) should have a contribution on decreasing the density of available oxygen vacancies with increasing the dopant content from BZY0.2 to BZY0.3 [3].
References
[1] S. Ushakov, A. Navrotsky, Appl. Phys. Lett. 87 (2005) 164103.
[2] M.D. Gonccedil;alves, R. Muccillo, Ceram. Int.40 (2014) 911-917.
[3] M.D. Gonccedil;alves, P.S. Maram, R. Muccillo, A. Navrotsky, J. Mater. Chem. A 2 (2014) 17840.

Electrical wind force is an important element in electrical switching behaviors of phase-change materials. It has been reported that the electrical wind force influences the motions of dislocations, which determines the degree of order-disorder states existing in phase-change materials [1]. In this presentation, we discuss electrical wind force-driven behaviors occurring in phase-change materials. At first, we report atomic mass-transport behaviors as DC voltage biases are applied in line-shape Ge₂Sb₂Te₅ (GST) devices. As the electrical current density reached 3-4 MA/cm² by DC voltage bias, a directional mass transport was identified by forming asymmetric surface morphology on the line-shape GST devices. By electric current, Joule-heating raised the temperature up to ~300 ^oC, implying that the mass transport of GST occurs in hexagonal phase (solid state) regime. In second, we extend the roles of electrical wind force to electrical switching behaviors of GST. We studied the effects of electrical voltage pulses on crystalline-to-amorphous phase transition of GST by in situ transmission electron microscopy (TEM). Electrical voltage pulse plays a critical role by creating dislocations through heat shock process: Rising edge of the pulse produces vacancies by heating, whereas during rapid cooling, atomic vacancies are condensed into dislocation loops. As the dislocations feel the electrical wind force, they become mobile and glide in the direction of hole-carrier motion. Continuous increase in the density of dislocations moving unidirectionally leads to dislocation jamming, which eventually induces the crystalline-to-amorphous phase transition. We interpret it through one-dimensional traffic model in which the increase of dislocation density exceeding a certain threshold point induces a catastrophic jamming of dislocations. Density functional theory (DFT) calculations of generalized-stacking-fault (GSF) energy show that basal plane of GST hexagonal phase provides favorable pathways of dislocation motions. Our understanding about dislocation-templated amorphization suggests that the transition from crystalline to amorphous states in phase-change materials may not require a melting process.
[1] S.W. Nam et al, Science, 336, 1561-1566 (2012)

Polymer nanocomposites (PNCs) and polymer-grafted “hairy” nanoparticles (HNPs) are of current interest for a wide array of mechanical, thermal and electrical applications, including energy storage in high energy density capacitors. For these nanostructured soft materials to be engineered for optimized property combinations such as high relative permittivity and high electrical breakdown strength, a detailed structure-property relationship must be constructed which builds upon quantitative, three dimensional morphology information and in-situ property characterization. The advantages of in-situ characterization are that it provides direct characterization of the material during operation in the end use application, and it has the potential for capturing dynamical information. Additionally, transient phenomenon or narrow phase windows can be captured which are difficult to observe using ex-situ techniques. We have been investigating structure property relations of PNCs and HNPs (polystyrene-silica) using transmission electron tomography, three dimensional reconstruction, and in-situ electrical testing. Electron tomography reconstruction using Model-Based Iterative Reconstruction was able to resolve the individual oxide nanoparticles with nanometer resolution, and their distribution within the polymer matrix. In-situ characterization was performed using electrical testing chips to probe electric field ranges from 0.1-10 V/micron and an in-situ probe holder apply fields in the range of 10-500 V/micron. Dielectric breakdown at high fields was observed in-situ, at fields which were comparable to ex-situ measurements on bulk films, and several interesting phenomenon were observed in the in-situ experiments pre- and post-breakdown. In-situ analysis of the nanodielectric material post-breakdown revealed significant morphological changes and chemical changes, which were quantified using tomography and electron energy loss spectroscopy and compared with FIB lift out ex-situ experiments on bulk films.

Linking catalyst structure with catalyst activity is a primary goal of much catalysis research. Observation of the catalyst structure at the atomic scale using environmental TEM (ETEM) while catalysis is taking place is a powerful technique for linking activity with structure. To do this well, it is essential to know the activity of the catalyst while it is being observed. This can be accomplished by measuring the gaseous products inside the ETEM using two complimentary techniques: electron energy loss spectroscopy (EELS) and residual gas analysis (RGA).
EELS and RGA both have advantages and drawbacks. EELS measures the gas immediately surrounding the sample, unlike the RGA, which is located some distance from the sample chamber, and must be differentially pumped. The RGA can monitor the gas composition continuously, even if there is no electron beam in the column, while EELS cannot be acquired at the same time as a TEM image. The RGA can detect smaller quantities of gas, while EELS is easier to quantify precisely.
We are applying the operando technique to determine structure-reactivity relations in Ru catalysts for CO oxidation. Though Ru for CO oxidation is a well-studied system, there is still debate in the literature regarding the most active state of the catalyst surface. Using a differentially pumped ETEM, the silica-sphere-supported Ru catalyst is initially either fully oxidized or reduced in-situ, and then heated in a stoichiometric mixture of CO and O₂ to a temperature at which we observe high CO conversion. A unique sample preparation method was developed to increase the amount of catalyst inside a Gatan Ta heating holder, thus maximizing the amount of product gas formed. Experiments are performed on both an FEI Tecnai and FEI aberration-corrected Titan.
We have observed that initially oxidized particles (RuO₂) have low activity even above 400^oC. At high temperature, these particles are reduced in-situ by the CO-O₂ reactant gas mixture and are subsequently more active for CO₂ production, as the temperature is ramped back down. Additionally, the particle morphology observed when the catalyst is highly active is similar to that observed at the same temperature in pure CO gas. The morphology in O₂ gas is markedly different, showing a Ru-core/RuO₂-shell structure. This suggests that under reaction conditions, the gas adsorbates are predominately CO, not O₂.
Aberration corrected microscopes dramatically increase the amount of detail observable on the surface of catalyst nanoparticles, but measures must be taken to keep particles as stable as possible during acquisition. Supports such as CeO₂ which are stable under the beam and show a strong metal-support interaction should decrease the movement of the Ru catalyst particles, allowing detailed analysis of surface facets and edges.
[1] This work was supported by The National Science Foundation (NSF-CBET 1134464).

Many energy and information storage processes, such as hydrogen storage, battery charging, and memory switching, rely on phase changes of nanostructured materials in reactive environments. Compared to their bulk counterparts, nanostructured materials appear to exhibit faster charging and discharging kinetics, an extended life cycle, and size-tunable thermodynamics.
However, in ensemble studies of these materials, it is often difficult to discriminate between intrinsic size-dependent properties and effects due to sample size and shape dispersity. Studies of hydrogen absorption in individual nanoparticles so far have been limited to nanostructures evaporated onto a substrate or to thin shells grown on a nanoscale core. In all these cases, however, there is limited control over the sample size and shape and the thermodynamics of hydrogen absorption is heavily influenced by the elastic interaction of the particle with the support.
Here, we present the first direct measurement of hydrogen absorption and desorption in individual colloidally-synthesized palladium nanocrystals, with sizes ranging from 29 nm down to 13 nm [1]. Our approach is based on in-situ electron energy-loss spectroscopy (EELS) in an environmental (scanning) transmission electron microscope.
By measuring the spectral position of the bulk plasmon resonance of individual palladium nanoparticles while varying the hydrogen pressure, we construct single-particle pressure - energy-loss isotherms. In contrast to ensemble measurements, in which sloped H₂ loading/unloading isotherms are observed [2], we find that palladium nanocrystals undergo sharp transitions between the α and β phases, with smaller particles loading at lower hydrogen pressures.
The observed size-dependence of the loading pressures can be understood by taking into account the elastic stress induced by the preferential hydrogen absorption at the surface of the nanocrystals. Such a surface-induced mechanism is similar to the one suggested for the intercalation of lithium in FePO₄ nanoparticles [3] and could be responsible for the mechanism of solute intercalation in a variety of nanostructured materials.
Our results provide a framework for the in-situ study of phase transitions in individual nanocrystals and highlight the importance of single-particle approaches for the characterization of nanostructured materials for energy storage.
[1] A. Baldi, T. C. Narayan, A. L. Koh and J. A. Dionne, Nature Materials AOP (2014)
[2] R. Bardhan et al., Nature Materials 12, 905-912 (2013)
[3] D. A. Cogswell and M. Z. Bazant, Nano Letters 13, 3036minus;3041 (2013)

Photovoltaics is conversion of light into electricity which takes place at atomic level, to further enhance performance of photovoltaic cells it is necessary to probe cells at atomic level which is now possible using Atom Probe Tomography (APT). APT can resolve materials and provide 3D atomic information at sub-nanometer level. Here we use this technique to understand and enhance efficiency of Silicon and Copper Indium Gallium Selenide (CIGS) solar cells by probing them at atomic level.
Photovoltaic is currently dominated by Silicon solar cells, and using ion implantation doping instead of standard diffusion process is a promising way to simplify the fabrication of silicon solar cells. However difficulties to form high quality boron (B) implanted emitters are encountered when implantation doses suitable for the emitter formation are used. This is due to a more or less complete activation of Boron after thermal annealing. Here we explain using APT results how different doping conditions change B distribution in Si at atomic level and systematically changes its emitter saturation current density.
CIGS is currently the most efficient solar cell (efficiency > 20%) under thin film category. This high efficiency is obtained for polycrystalline CIGS due to Na atoms (diffused from the glass substrate) segregation along Grain Boundaries (GBs). This increased efficiency due to presence of GBs is both surprising and interesting; to understand the role of GBs in changing the electrical properties of CIGS advanced characterization techniques like APT must be used. Herein we combine EBSD (Electron Back Scattered Diffraction) to locate GBs and APT to explore nano-chemistry of GBs in CIGS for different Ga concentrated samples. Results show that: composition profile at GBs strongly depends on Ga ratio (Ga/In+Ga). Depletion and enrichment in Cu conc. is observed at GB for Ga poor and Ga rich samples respectively, suggesting different phase compositions at GBs for different Ga ratios. Efficiency variation of CIGS for different Ga concentration is linked for the first time with its GB composition profile will be discussed.

The understanding of energy storage materials properties is of great interest in academia and industries. The complex interplay of bulk and interface properties determines the overall properties, but it is still challenging to discriminate intrinsic grain from intergrain properties. Therefore, it would be highly desirable to probe the properties of individual grains, which are typically nanoscale building blocks in the context of its macroscopic environment or assembly. Hence, probing the charge transport e.g. of individual nanocrystals in a macrosized functional electrode or of individual nanowires in a 3D assembly would be of great interest.
In this work we demonstrate the feasibility of a highly flexible four-probe nanorobotics setup, which allows local charge transport measurements with high spatial resolution on real world samples under scanning-electron microscopic inspection. We will illustrate the effect of grain boundaries of different energy storage materials on the charge transport on nanostructured surfaces exhibiting nanocrystal domains.

With advances in high resolution imaging in (scanning) transmission electron microscopy and scanning probe microscopies, precision measurements (10 pm or better) of atomic positions are routinely obtained. This level of fidelity is sufficient to correlate bond length (and hence energy), as well as bond angle, to functional properties of materials. We introduce an approach for local analysis of material structure based on statistical analysis of individualized, local atomic neighborhoods. Both supervised and unsupervised learning algorithms are used; this allows for a highly flexible framework of specified metrics which in turn are sensitive various lattice aspects. Using the local neighborhood approach we demonstrate phase identification as well as unit cell identification and classification. Multiphase catalytic materials, complex oxides and 2D materials are presented as case studies. Furthermore approaches for building image genomes and structure-property libraries, based on conjoining structural and spectral realms through local atomic behavior are discussed.

MXenes, a recently discovered large family of two-dimensional (2D) early transition metal carbides and carbonitrides, have shown much promise in electrochemical energy storage applications, such as battery and supercapacitor electrodes. We recently reported on large volumetric capacitance and high rate capabilitiy of Ti₃C₂T_x - the most studied MXene to date. Spontaneous intercalation of a variety of single- and multiply charged cations, together with highly reversible electrochemical insertion of the same cations, has been well documented for Ti₃C₂T_x in aqueous electrolytes. Perfect capacitive behavior was observed for Ti₃C₂T_x MXene even at quite high charge and discharge rates, contradicting to slow intercalation of ions in a specific potential range, which is usually observed in layered materials for battery applications.
In order to understand mechanism of capacitance in MXenes we performed characterization of the mechanical deformations of MXene electrode materials at various states-of-charge with a variety of cations (Li, Na, K, Cs, Mg, Ca, Ba, and three tetrashy;alkylammonium cations) during cycling by electrochemical quartz-crystal admittance (EQCA, quartz-crystal microbalance with dissipation monitoring) combined with in situ electronic conductance and electrochemical impedance. Based on this work, it appears that in MXenes cationic insertion is accompanied by significant deformation of the Ti₃C₂T_x particles, that occurs so rapidly so as to resemble 2D ion adsorption at solid-liquid interfaces. The latter is greatly facilitated by the presence of water molecules between the MXene sheets.
References.
M. R. Lukatskaya, O. Mashtalir, C.E. Ren, Y. Dall&’Agnese, P. Rozier, P. L. Taberna, M. Naguib, P. Simon, M.W. Barsoum, Y. Gogotsi, “Cation Intercalation and High Volumetric Capacib tance of Two-dimensional Titanium Carbide” Science, 2013, 341 (6153), pp. 1502-1505
M. D. Levi, M. R. Lukatskaya, S. Sigalov, M. Beidaghi, N. Shpigel, L. Daikhin, D. Aurbach, M. W. Barsoum, Y. Gogotsi, “Solving the Capacitive Paradox of 2D MXene by Electrochemical Quartz-Crystal Admittance and in situ Electronic Conductance Measurements” Advanced Energy Materials, DOI: 10.1002/aenm.201400815

Stability and availability of efficient catalysts at the cathode of proton exchange membrane fuel cells (PEMFC)s is a critical challenge in their commercialization. Nanoalloy catalysts are an attractive solution because these materials not only reduce the amount of Pt usually required for efficient PEMFC operation but also exhibit improved stability and selectivity. Once nanoalloys composition - atomic-level structure - catalytic properties relationships are revealed and understood well nanoalloys synthesis can be steered toward more efficient operation in PEMFCs on a rational and not trial-and-fail basis. In this respect studies on changes in the atomic-level structure of nanoalloy catalysts under realistic operating environment are particularly valuable. We will report results from recent in situ high-energy synchrotron x-ray diffraction and atomic pair distribution function studies on ternary Pt-Ni-Co and binary Pt-Co and Pd-Ni alloy catalysts at the cathode of a PEMFC designed so that interference from cell&’s anode, membrane and encasing is minimized. In situ data indicate that the increased integrity of ternary nanoalloys at atomic level contributes significantly to their superior performance.

Ambient pressure X-ray photoelectron spectroscopy (APXPS) is a valuable tool for the investigation of surfaces under operating conditions. Most experiments require the quantitative determination of the chemical composition of the sample, often as a function of probing depth, which can be varied in synchrotron-based APXPS by changing the incident photon energy and thus the electron kinetic energy. To determine the precise elemental composition over a wide range of kinetic energies it is essential to use experimentally measured sensitivity factors for the core levels of interest. Recently it has been reported that intramolecular inelastic scattering processes can lead to deviations from the expected relative intensities of core level peaks. [1] A common method for the determination of C1s-to-O1s sensitivity factors in APXPS is the measurement of gas phase CO or CO2 spectra, where the sensitivities can in principle be determined from the known stoichiometry of the molecule and the measured C1s and O1s peak areas. Here we present relative C/O sensitivity factors determined from CO and CO2 gas phase spectra over the kinetic energy range from 30 eV to 800 eV and discuss their validity for determining the C/O stoichiometry at surfaces.
[1] J. Söderström et al., Nonstoichiometric Intensities in Core Photoelectron Spectroscopy, Physical Review Letters 108, 193005 (2012).

Control of magnetic properties in ferromagnetic materials has been an overarching goal for potential applications in magnetic storage and spintronics devices. In this work we report reversible reduction in coercivity of Co/Pd multilayer thin films under high density DC biasing. We carried out in-situ focused MOKE measurement while the specimen is under DC bias. These experiments show a reduction in coercivity during the application of direct current. We propose this reduction is results from the electromigration induced stresses and resulting grain rotation.

Electrocatalytic chemical conversion reactions are an attractive source of alternative energy when used in fuel cell or electrolysis applications. While substantial progress has been made over decades of research, wide-spread utility of electrocatalytic power conversion or chemical synthesis is still limited on a commercial scale. A lack of understanding fundamental structure/function relationships, particularly during catalytic events, is a significant hurdle limiting rational catalyst development and commercialization. In this work, high-energy X-ray diffraction (HE-XRD) coupled with atomic pair distribution function (PDF) analysis along with X-ray absorption spectroscopy (XAS) are performed during electrocatalytic methanol oxidation to determine voltage dependences on local chemistry and structural order. EXAFS provides critical element-specific chemical and structural information within the first coordination sphere, which PDF analysis provides additional structural details over a larger size scale (~ 4 nm). Performing these experiments during electrocatalytic methanol oxidation yields structural insights that are used to assess catalytic properties that are lacking from ex-situ experimentation. Examples will include monometallic Pt and Pd nanoparticles, along with bimetallic PdAu and FeNi catalytic systems.

Zinc oxide semiconductors have received great attention because of their desirable properties such as a wide band gap of 3.37 eV, high exciton binding energy at room temperature, good conductivity and high transparency in the visible region [1]. These features make ZnO thin films highly suitable for room temperature ultraviolet optoelectronic devices and transparent conductive electrodes in solar cells. Deposition of such thin films by the atomic layer deposition (ALD) method [2] has attracted increasing interest due to the ability to produce conformal material layers with thickness in the nanometer range. Deposition on Si substrates is particularly interesting for integration with standard microelectronics. However, despite the many successes of ZnO growth by ALD, the growth mechanism in the early stages is still not sufficiently understood. So far, by means of in situ synchrotron X-ray scattering and fluorescence, Fong et al. suggested that ZnO films grow as islands on Si substrate at the initial stage [3]. However, the nucleation process and detailed structure of the ZnO films during the first ALD cycles has not been addressed yet.
In this work, by using in situ X-ray absorption spectroscopy in combination with ab initio simulations of the near Zn K-edge absorption cross section (XANES), we address the detailed local structure of the incipient growth of ZnO thin films during the very first ALD cycles. Zn K-edge XANES were simulated using a full-potential finite differences approach. A good agreement between the simulated Zn K-edge XANES spectrum for bulk wurtzite ZnO and the experimental spectra starting from the second ALD cycle indicates that ZnO films with the expected wurtzite type structure and high structural order are formed very soon in the growth process. In contrast, the Zn K-edge XANES spectrum of the ZnO film acquired at the end of the first cycle is considerably different. Very good agreement was found between this experimental spectrum and a XANES calculation performed using a model with O atoms in the first atomic shell around Zn, and a second shell containing Si atoms, in a local symmetry similar to the one of the hemimorphite structure. Preliminary thermodynamic calculations suggest that hemimorphite is a stable form under the experimental conditions (pressure, temperature, etc.) of the first cycle.
This present work is, to the best of our knowledge, the first X-ray absorption investigation ever performed during ZnO thin films growth and the overall findings provide a deeper understanding of the initial nucleation stages of ZnO and bonding to the Si substrate during the ALD process.
References
S. J. Pearton et al. Prog. in Mater. Science 50, 293 (2005).
T. Tynell et al.Semicond. Sci. Technol. 29, 043001 (2014).
D. D. Fong et al.Appl. Phys. Lett.97, 191904 (2010).

The extreme conditions found in many energy-related applications often demand the development of new compositions and phases of materials, and the assessment of their kinetic behavior. One way to precisely tune the crystal structure and stoichiometry of thin films is through solid-state diffusion. This method is relatively unexplored, yet intriguing for tuning film properties and in understanding the thermal behavior of solids exposed to extreme conditions. Metal silicides (Me_xSi) are a particularly interesting class of materials which can be formed through solid-state diffusion. They are widely used industrially, including in many energy applications, due to their rare combination of thermal stability, mechanical robustness, and metallic electrical properties. Applications of Me_xSi include Ohmic contacts, gate electrodes, local interconnects, and in thermoelectric devices. Despite this, the lack of fundamental understanding of the relevant solid-state diffusion processes limits the ability to tune the crystal structure, stoichiometry, and the resulting properties for Me_xSi thin films.
Here, we explore both source-limited and kinetically-limited solid-state diffusion as two routes to tune the stoichiometry of platinum silicide (Pt_xSi) thin films #8210; a popular Me_xSi that is of specific interest for applications under extreme conditions, including as nanoelectrical contacts for energy-efficient computing. Source-limited solid-state diffusion uses the precise control of the precursor thin film layer thicknesses, which predetermine the achievable silicide stoichiometry after annealing. Kinetically-limited solid-state diffusion utilizes a precisely controlled time-temperature regime to obtain the desired silicide stoichiometry and phase. We sputter-coated silicon nitride transmission electron microscope (TEM) support grids with thin layers of amorphous silicon (a-Si) and platinum (Pt). Using in situ heating experiments inside a TEM while performing real-time electron diffraction we showed that both diffusion routes lead to stoichiometrically-controlled formation of Pt_xSi (x = 1, 2, 3) thin films with high phase selectivity. We determined the crystal structure and formation sequence for all three phases. Subsequent ex situ and in situ X-ray photoelectron spectroscopy (XPS) analysis determined the film stoichiometry and confirmed the phase selectivity.
The results demonstrate, for the first time, that: (1) the diffusion processes during Pt_xSi-formation using sequentially-deposited layers of Pt and a-Si significantly differs from the well-studied Pt/single-crystal silicon system; and (2) the formation of Pt₃Si. This Pt-rich phase has not been reported elsewhere and is especially attractive for applications. Overall these results highlight the opportunity that a precise control of the solid-state diffusion process presents in accessing novel applications fields by tailoring the stoichiometry and crystal structure of thin films.

Imaging in liquid at the enhanced resolution with nanoscale or atomic levels inside a transmission electron microscope (TEM) shows great promise for the real time study of liquid phase reactions. A capsulated liquid cell is usually composed of ultra-thin Si₃N₄ windows and holds a <500 nm thick liquid layer in between.^1,2 In a regular liquid cell, all the reactants are pre-mixed in the cell and the reaction can be observed only after introducing the cell into TEM. It limits the type of reactions that can be studied. The reaction cannot be too fast or too slow for two major reasons: 1) the rapid reaction might occurs outside during assembling a liquid cell, which takes significant amount of time to complete, and 2) to observe the entire slow reaction, long exposure time is required. It turns out that electron beam irradiation can largely alter solution chemistry due to various effects such as heating, charging and production of free radicals.³
In this talk, we report an observation of the corrosion behavior on Pt nanoparticles. The experiment is enabled using a fluid liquid cell designed by Hummingbird Scientific. This setup enables the study of rapid reaction by pumping the reactants into the liquid cell after the introduction of the cell into TEM. Then the initiation of the reaction can be observed during TEM observation. Various shapes of Pt nanoparticles, which were previous reported,^4-6 are chosen to study the etching behaviors of Pt nanoparticles during the corrosion process. With the high time resolution under TEM observation, the kinetics of Pt surface etching could be studied.
1. M. J. Williamson, R. M. Tromp, P. M. Vereecken, R. Hull, F. M. Ross, Nature Materials 2 532 (2003)
2. H. Zheng, R. K. Smith, Y. W. Jun, C. Kisielowski, U. Dahmen, P. A. Alivisatos, Science 324, 1309 (2009)
3. J. M. Grogan, N. M. Schneider, F. M. Ross, H. H. Bau, Nano Lett. 14, 359 (2014)
4. W. Zhou, J. B. Wu, H. Yang, Nano Lett. 13, 2870 (2013)
5. J. B. Wu, L. Qi, H. J. You, A. Gross, J. Li, H. Yang, J. Am. Chem. Soc., 134, 11880 (2012)
6. J. B. Wu, A. Gross, H. Yang, Nano Lett., 11, 798 (2011)

Most research conducted in hydrogen transport membranes (HTMs) is currently focused in the areas of separation technologies and characterizations of hydrogen fluxes. No significant work has been performed on thermo-mechanical properties of HTMs at elevated temperatures and/or under various chemical environments. The effect of thermal cycles or thermal shock on the mechanical properties and the stability of the membranes are also very critical. This paper will present the thermal shock behaviors of a novel hydrogen transport membrane (HTM) cermet. In order to study the effects of the thermal shocks, the samples were soaked in air in a customized thermal cycling rig in the temperature range between 50-850°C. Scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) was used to visualize the microstructural morphology changes in the magnification up to 10000X and analyze chemical composition of the specimen by X-ray spectrum acquisition and X-ray mapping. Elemental composition analysis and semi-quantitative analysis of the HTM after 120 and 500 thermal cycles were performed by the techniques of X-ray florescence (XRF) and the electron microprobe that is equipped with EDAX energy dispersive spectrometers (EDS). Both SEM and Microprobe analysis show that the temperature gradient during thermal cycling produced more micro-cracks inside the HTM Disc, whereas the chemical reaction between Pd and Oxygen to form PdO disturbed the continuity of Pd-YSZ dual interconnection system from surface down. As the treatment of thermal cycling increased from 0 to 500 cycles, the mass fraction of Pd is greatly reduced from 74% to 12%, whereas, increased amount of PdO is produced by the oxidation of Pd with O₂. The other zirconia phases, including both M-ZrO₂ and YSZ, did not change significantly with the treatment of up to 500 thermal cycling between 50 to 850°C.

The synergy among different disciplines in the field of nanotechnology is giving much impulse to hybrid organic/inorganic nanocomposites to tailor functional properties. A class of hybrid nanocomposites can be obtained by combining polymeric materials and inorganic nanocrystals for their peculiar electronic, optical and catalytic properties due to quantum-size effects.
Our interest towards nanocrystal/polymer nanocomposites is motivated by their application in hybrid devices. In particular,we have synthesized II-VI semiconducting nanocrystals (NCs) within a polymer matrix thus avoiding ex-situ blending procedures that may have agglomeration and phase segregation as main drawbacks. The synthesis process of the NCs (here camdium sulfide, CdS) involves the addition of a metal precursor to a polymer in solution and spin coating of the blend. A thermal treatment of the deposited film causes the decomposition of the precursor and the CdS NCs growth within the polymer. In bulk films obtained by drop casting we found that the nanoparticle size and aggregation depend upon the annealing conditions, namely temperature and duration of the treatment. Morevoer, the same process works with both amorphous insulating polymers as polystyrene and topas and semicrystalline conjugated polymers such as P3HT employed in hybrid solar cells. We believe that the device performance can be greatly improved if the growth and dispersion of the NCs within the polymer matrix are carefully controlled since the very first stages of their formation.
In this work we describe both ex-situ and in-situ experiments of grazing incidence diffraction (GID) and grazing incidence small angle scattering (GISAXS) under different annealing conditions on thin films (20-30 nm) performed at beamline ID01 at ESRF. While during the ex-situ experiments the crystalline signal from the NCs was weak and hardly detectable, the in-situ studies gave very different results. 2D GISAXS images showed that the precursor crystal structure changed by effect of the temperature above 100°C. At 150°C new diffraction peaks arranged in hexagonal symmetry were observed, corresponding to a distance of about 2.7 nm. This peculiar diffraction pattern became very well defined at 170°C. Correspondingly, at 170°C GID scans showed strong crystalline peaks from cubic CdS NCs of about 2 nm size. With increasing temperature, these peaks become more intense and sharper. These results indicate that at 170°C the QDs are close packed and regularly arranged in an hexagonal 3D lattice with lattice parameter of 2.7nm. Such ordered state disappears for annealing above 220°C. The main results is that a temperature of 170°C is sufficient to synthesize the CdS NCs in thin polymeric films, while in the bulk system a higher temperature by at least 30°C is needed. Reducing the annealing temperature prevents the degradation of the polymer matrix and represents an important issue for the device realization and performances.

Photocatalysts have potential applications for solar fuel generation either through water splitting or CO₂ reduction. The Ni/NiO core/shell structure is one of the most efficient co-catalysts for solar water splitting when coupled with suitable semiconducting oxides. However, Ni/NiO core/shell structures on TiO₂ are only able to generate H₂ but not O₂ in aqueous water. It is now recognized that atomic level in situ observations are critical for understanding the structure-reactivity in photocatalysts in the presence of reactant and product species and during in-situ light illumination. Herein we use TiO₂ as a model material to develop in situ photocatalytic experimental methodology and explore structure changes of Ni/NiO core/shell on oxide semiconductor photocatalysts. Here we employ a modified ETEM with a broadband light source to study the nature of the hydrogen evolution reaction in these systems correlating photochemical H₂ production with atomic resolution structure.¹ During the H₂ evolution reaction, the metal core initially formed partial voids which grew and eventually all the Ni diffused out of the core-shell into solution leaving an inactive hollow NiO void structure. This photocorrosion occurred either due to direct contact with the water through cracks or a Kirkendall effect where Ni diffused along grain boundaries in the NiO shell onto the particle surface where dissolution took place. This observation is also achieved ex-situ when exposed to gas phase water vapor. In situ characterization is utilized to explore the possible photo induced Ni diffusion and oxidation when exposed to water vapor and light. In-situ heat treatment in H₂ or O₂ is applied to prepare initially Ni/TiO₂, NiO/TiO₂ or NiO-Ni-TiO₂ materials in an environmental transmission electron microscope (ETEM). Then, without exposure to air, analysis can be performed in the same modified ETEM under in situ conditions in the presence of light and reactants to explore oxidation/reduction or interface changes under photocatalytic water splitting conditions. The detail morphology and mechanism of the photocorrosion of Ni metal will be discussed.
Reference
[1]. Miller, B.K.; Crozier, P.A. Microscopy and Microanalysis 2013, 19, 461-469
[2]. The support from US Department of Energy (DE-SC0004954) and the use of ETEM at John M. Cowley Center for HR Microscopy at Arizona State University is gratefully acknowledged.

A hybrid glass was molecularly designed and the synthesized by the insertion of a long alkyl chain in the polymeric network. Chromium nanoparticles were also doped into the hybrid glassy host. TEM images of the doped hybrid glass revealed a novel nano-fringe pattern. The nano-periodic structure shown in TEM images contributes to create 'diffraction grating' when the light passes through the long carbon-chains. The doped hybrid glass also exhibits an unconventional optical property, photo-refraction modulated by acoustic waves. The most striking observation from the doped glass is acoustically coupled photorefraction, which is in a centrosymetric material and thus does not require the application of static electric fields or polling during material synthesis. Implicit in such behavior is fast response photo-refraction, which is ascribed to the density-controlled mobility of electrons trapped in aligned nano-domains of the hybrid glass. Usually, solid media generate the linear waves due to rigid solid lattice frames. Interestingly, the doped hybrid glass generates a large acoustic wave due to the effective optical grating at the molecular scale.&’ The doped glass showed a strong ‘acoustic response&’ as much as a liquid. In laser experiment, we calculated ‘coefficient of phonon diffraction (D),&’ which is proportional to the coefficient of thermal conductivity. The number (D) was FIVE times smaller than that of normal glasses; the thermal conductivity of the glass is FIVE times less than that of normal glasses. Therefore, the doped hybrid glass serves as a ‘heat generator,&’ which the HEAT ENERGY gets transferred into expansion or compression wave (acoustic waves) effectively.

Combustion of fossil fuels is one of the major emission sources of the greenhouse gas including water vapor, CH₄, NO_x, O₃, and especially CO₂. Therefore, it is necessary to develop technologies which can mitigate CO₂ emission while allowing us to utilize fossil fuels. Even though there has been extensive research on CO₂ capture properties of various alkali and alkaline-earth metal oxide such as MgO, CaO, and LiZrO₂ due to their strong basic nature, there has been little work done on CO₂ absorption-regeneration mechanism how the real absorption and regeneration take place on the gas (CO₂)-solid (absorbent) interface depending on given process conditions (temperature, pressure, and atmosphere). In this study, we utilize environment TEM in order to see any morphological and crystallographical changes at interface of absorbate (CO₂) and absorbent (alkali or alkaline-earth metal oxides) during temperature swing absorption (TSA) CO₂ capture process. Quantum mechanical calculation by using density function theory (DFT) was introduced to understand CO₂ absorption mechanisms on various interfaces from adsorption energies as well as electronic properties including density of states and Mulliken population analysis of the interaction between the absorbed CO₂ molecules and the surface of sorbents in the three dimensional periodic-slab models. Geometry optimizations were reliably carried out using DMol³. We have successfully synthesized uniform-sized magnesium oxide and calcium oxide in the range of 10 to 50 nm by simple sol-gel method followed by hydrothermal treatment. The synthesized absorbents were characterized by ICP-AES, XRD, XPS, STEM, and N₂ adsorption and desorption. Both total CO₂ capacity and 90% breakthrough CO₂ capacity was examined by thermogravimetric analysis and packed-bed flow reactor system, respectively. From the results, the synthesized MgO and CaO absorbent showed high CO₂ absorption performance comparable with previously reported values. For the in-situ TEM analysis, we successfully applied heat and CO₂ through customized wire-shaped grid in order to mimic the lab-scale TSA CO₂ capture process. Consequently, we could observe dramatic particle expansion and surface growth originated from fast Mg²⁺, Ca²⁺, and O^2- ions transport from the bulk to surface probably due to liquid-like behavior of MgO and CaO absorbent. The other characterizations and quantum mechanical calculations by density function theory (DFT) were evaluated to clearly support those morphological and crystallographical changes and will be discussed in the present study. We believe this first in-situ observation of CO₂ absorption phenomena and integrated mechanism study would be helpful to design other energy and environment materials.This work was supported by KCRC through the NRF funded by Ministry of Science, ICT, and Future Planning (NRF-2014M1A8A1049258)

Silicon (Si) has been widely investigated to develop high energy density anodes for next generation lithium ion batteries (LIBs) due to its unparalleled specific capacity near 10 times higher than commercialized graphite ones. However, more lithium (Li) insertion/extraction into/from Si causes large morphological and volumetric changes during cycling, and these result in undesirable failure or fracture of the active material leading to severe capacity degradation. It is one of the biggest challenges for replacing the existing anodes with Si.
Meanwhile, recent real-time observations and analyses have provided invaluable information on the volume expansion of Si nanomaterials during their alloying reactions with Li and have thus served as useful bases for robust design of high capacity Si anodes in LIB. In an effort to deepen the understanding on the critical first lithiation of Si, especially in realistic liquid environments, herein, we have engaged in situ graphene liquid cell transmission electron microscopy (GLC-TEM). GLC-TEM is a new combination of the liquid-encapsulating graphene cell and conventional TEM for real-time observation of specimen in liquid. In present study using this technique, chemical lithiation is stimulated by electron-beam irradiation, while the lithiation process is being monitored by TEM in real time. The real-time analyses informing of the changes in the cross-sectional dimensions indicate that the very first lithiation of Si nanoparticle shows anisotropic volume expansion favoring the <110> directions due to the smaller Li diffusion energy barrier at the Si-{110}/electrolyte interface. Once passing this initial volume expansion stage, however, Li diffusion rate becomes isotropic in the inner region of the Si nanoparticle. As a unique characterization capability, the GLC-TEM has revealed novel phenomena during lithiation of Si nanoparticles, such as preferential lithiation onset along certain crystal orientations followed by isotropic lithium diffusion in the inner regions of the nanoparticles, which has been unseen from the previous in situ analyses. Furthermore, the current study suggests that the in situ GLC-TEM technique can be a useful tool in understanding battery reactions of various nano-sized active materials, particularly those whose initial lithiation plays a pivotal role in overall electrochemical performance and structural stability of the active materials.

Nuclear graphite, usually used as a moderator in the reactor core, is a typical quasi-brittle material. It is usually multi-phase, aggregated and porous, and the microstructure has a hierarchy characteristic. The microstructure is further modified by neutron irradiation and radiolytic oxidation when CO₂ is used as coolant, which leads to reduction in strength, distortion and fracture of the core. Unirradiated graphite has a non-linear stress-strain response because of distributed damage arising from fabrication and damage accumulation within the material prior to rupture. There is no evidence that these graphites can be plastically deformed. Hence, changes in compliance, together with any deviation from an initial linear load-displacement response are attributed to localised micro-cracking within the process zone that are a precursor to macro crack formation. Our previous research has shown that for Pile Grade A (PGA) nuclear graphite subject to a four-point bending load, the process zones are heterogeneously formed on the tensile side, and macro-scale cracks form when a zone reaches a critical size of ~3 mm. The occurrence of damage within the process zones results in the relaxation of local constraints, therefore, the size of these regions can be characterised by the examination of the lattice strain developed with applied strain in a deformed material.
In the present work, we consider a Gilsocarbon graphite that is used in operating advanced gas-cooled nuclear fission reactors in the UK, and it is also considered as a potential candidate for future Gen IV designs. We characterise the damage development in this material in situ under bend loading at two length-scales using two different approaches.
(i) The Gilsocarbon specimens are in the form of beams (10mmx20mmx150mm), subject to four point bending when tested in situ at a neutron beamline, ENGIN-X, ISIS in the UK. Six positions across the mid-section from tensile to compression was measured by neutron diffraction at each loading condition. It was found that the lattice strain changes linearly with applied bulk strain but the magnitude is one order less. This relationship deviated from linear when the applied deformation exceeded about two thirds of the peak strain.
(ii) Micro-scale cantilever beams prepared by focus ion beam milling, typically with the dimension of 2x2x10 µm, were loaded in situ by a force measurement system in a Helios Dualbeam Workstation. The damage evolution was viewed throughout under the scanning electron microscope to establish the role of the nano-scale pores within the graphite. These results are typical of the damaged micro-scale fracture that occurs within an individual process zone.
The results obtained from the two approaches are discussed with respect to the characteristics of the strain accumulation within individual process zones and the formation of micro-cracks in this quasi-brittle nuclear graphite.

Through in situ quartz crystal microbalance (QCM) monitoring, we resolve the growth of a self-assembled monolayer (SAM) and subsequent metal oxide deposition with high resolution. We introduce the fitting of mass deposited during each atomic layer deposition (ALD) cycle to an analytical island-growth model that enables a time-efficient and high-resolution method to quantify growth inhibition, nucleation density, and the uninhibited ALD growth rate. A long-chain alkanethiol was self-assembled as a monolayer on gold- coated quartz crystals in order to investigate its effectiveness as a barrier to, or nucleation reducer for, ALD. Compared to solution-loading, vapor-loading is observed to produce a SAM with equal or greater inhibition ability in minutes vs days. The metal oxide growth temperature and the choice of precursor also significantly affect the nucleation density, which ranges from 0.001 to 1 sites/nm2.
Based on these studies, we find further evidence to support a defect/pinhole mechanism that in at least one case points to an unexpected dependence on ALD precursor choice.

An understanding of the materials transformation and interfaces in electrochemical processes is critically important for identifying the failure mechanism or improving the lifetime of batteries and other relevant devices. In-situ transmission electron microscopy, which allows for real-time imaging of electrochemical processes in realistic liquid electrolyte environments with high spatial and temporal resolution, has attracted significant attention. Here, we report direct visualization of electrochemical lithiation and delithiation of MoS₂ nanosheets in commercial LiPF₆/EC/DEC electrolyte for lithium ion batteries utilizing electrochemical liquid cell TEM. With lithium metal particle and MoS₂ nanosheets loaded on left and right side of Ti contact electrode, respectively, the current-voltage curve was recorded simultaneously during the charge cycles, the real time observing of MoS₂ dynamic reaction reveals the dissolution of MoS₂ in voltage range of 1.8 ~ 1.2 V, and these kinds of reactions is attribute to irreversible decomposition. Based on the combined in situ and ex situ studies, we discussed the reaction mechanism of transformation in detail. The results shed light on better understanding the fundamental lithiation mechanism in MoS₂ and strategies of improving electrode design for improving the performance of MoS₂ as anode for lithium ion batteries.
Electron Microscopy (NCEM) of the Lawrence Berkeley National Laboratory, which is supported by the U.S. Department of Energy (DOE) under Contract No. DE-AC02-05CH11231. HZ thanks the funding support from U.S. DOE Office of Science Early Career Research Program.

Fuel cells and supercapacitors are electrochemical devices expected to secure efficient production and transformation of electricity. Notwithstanding their environmental appeal, the widespread application of these devices is still hindered by materials-science problems, chiefly related to the limited durability of crucial functional components. In this regard, the development and implementation of appropriate methods for in-situ characterization of the components of the energy-conversion devices at the functionally relevant length and time scales is highly required. The complementary capabilities of synchrotron-based x-ray microscopes in terms of imaging, spectroscopy, spatial and time resolution and variable probing depths have opened unique opportunities to explore the structure and chemical composition of these technologically relevant complex materials and correlate them to the actual operating conditions [1]. The most important achievements in this respect will be illustrated by selected results from recent studies of functional materials, as electrocatalysts and supercapacitors [2, 3], and simplified versions of externally-driven [1, 3-5] and self-driven [6] devices exploring the morphology and composition as a function of growth and working conditions. Monitoring in-situ the lateral distribution of the chemical state and local potential at the electrode/electrolyte interface, as well as mass transport and contamination phenomena, has allowed us to gain insight into electrochemical and chemical processes and structural changes taking place in energy conversion systems and correlate them to their properties and stability under actual operation conditions.
[1] B. Bozzini et al,, Chem. Eur. J., 18, 2012, 10196.
[2] P. Bocchetta et al, Electrochimica Acta 2137, 2014, 535-545.
[3] B. Bozzini et al, ChemElectroChem 1, 1-9 (2013).
[4] B. Bozzini et al, ChemSusChem 4, 1099 (2011).
[5] Won H. Doh et al, ChemElectrChem 2013 DOI: 10.1002/celc.201300134.
[6] B. Bozzini et al, J. Phys. Chem. C, 2012, 116, 23188.
[7] B. Bozzini, M. Amati, L. Gregoratti, and M. Kiskinova, Scientific Reports, DOI: 10.1038/srep02848 (2013).

A knowledge-based approach towards developing a new generation of solar energy converting devices requires a fast and direct feedback between sophisticated analytics which can probe thin-layer and interface properties with both lateral and in-depth resolution on the nanometer scale and state-of-the-art processing facilities for all relevant material classes. A promising approach is the coupling of synchrotron-based X-ray characterization techniques - such as X-ray photoelectron spectroscopy and -microscopy (XPS/XPEEM), as well as X-ray diffraction (XRD), absorption (XAS) and emission/fluorescence (XES/XRF) spectroscopy, providing the unique possibility to map the electronic and chemical structure of thin layers and interface regions - with relevant in-system/in-situ sample preparation in one dedicated vacuum system. In a concerted effort, the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB) and the Max Planck Society (MPG) will develop, install, and operate EMIL, the Energy Materials In-situ Laboratory, a unique facility at the BESSY II synchrotron light source in Berlin, Germany. EMIL will be dedicated to the in-situ and in-operando X-ray analysis of materials and devices for photovoltaic applications and of (photo)catalytic/photo-electrochemical processes. EMIL is designed such that it can serve up to three experimental end-stations that each can simultaneously access soft and hard X-rays in an energy range of 80 eV - 10 keV, and comprises all characterization and deposition facilities in one integrated ultra-high vacuum system. In addition, a fourth end station is planned for dispersive XES using high flux radiation of 2-10 keV. EMIL will study solar energy converting devices including photovoltaic (PV) structures based on silicon- and compound semiconductors, hybrid organic/inorganic heterojunctions, and the emerging organo-metal halide perovskites. Furthermore, new electrode materials for photoelectrochemical fuel production and respective catalysts will be studied in-operando. One focus of the research that will be performed at EMIL is the comprehensive characterization of nanomaterials and hybrid structures with available synchrotron-based characterization methods as well as complimentary laboratory-based techniques available at EMIL as well. These nanostructured and hybrid materials will be relevant for thermoelectric applications, solar cells, catalysis, new battery materials and hydrogen storage. Thus, EMIL will serve as a research platform for national and international collaboration in the field of photovoltaic/photocatalytic energy conversion and beyond. In this presentation, we will provide an overview of the analytic capabilities of the EMIL endstations and the attached thin-film deposition facilities.

Heterogeneities in batteries are significant drivers for degradation and failure. We use LiFePO₄, a phase-separating positive electrode, as a model system to investigate the origins of electrochemical heterogeneities at the single particle and porous electrode length scales. There have been conflicting reports on single-phase vs. two-phase intercalation pathways in individual particles, as well as on sequential vs. simultaneous intercalation at the electrode level.
In this work, we developed a suite of nanoscale X-ray imaging techniques to map the distribution of Li in a porous electrode. First, we employed ex situ single-particle spectro-imaging to show that the electrochemical current in an electrode is increasingly homogeneous at higher cycling rates, which contrasts with conventional transport-limited models. This arises from a competition between the thermodynamic transformation barrier in phase-separating materials and the kinetics of inserting and removing Li from a particle [1]. We further confirmed such findings by developing an operando platform to image, in real time, a cycling battery electrode containing standard organic electrolytes at sub-100 nm resolution. We also tracked lithiation in individual particles as they cycle electrochemically, and observed that lithiation within a single particle deviates from both the conventional single-phase and two-phase intercalation pathways. We propose that this behavior arises from topological defects in the particles, as well as spatial inhomogeneities in the reaction rate along the particles&’ surfaces. Understanding and controlling for heterogeneity across nanometer to micron length scales could significantly enhance the durability and lifetime of Li-ion batteries.
(1) Y. Li, et al. “Current-induced transition from particle-by-particle to concurrent intercalation in phase-separating battery electrodes,” Nature Mater., Advanced Online Publication, 2014 doi:10.1038/nmat4084

In-situ experiments are finding increased use to explore the relationships between material processing methods, microstructure and functional properties. TEM and X-ray microscopy can provide valuable information about changes in microstructure and chemistry of materials with high spatial resolution during in-situ experiments. Recently the ability to image in liquid in both TEM and X-ray microscopy has been enabled with the advent of new liquid cell sample holders. Observing solid-liquid interfaces with high resolution and spectroscopy capabilities is important for comprehension of physical and chemical interactions between material and liquid. This is particularly important for the study of liquid-electrochemical processes, where a more detailed knowledge of the solid-liquid interactions can substantially improve our understanding of the degradation of materials inside energy storage devices. Here we present a method for liquid cell TEM and X-ray microscope characterization of nano-scale energy materials and initial results from characterizing electrochemical processes in battery systems. TEM characterization was performed during SEI formation from LiPF₆ in EC:DMC. The in-situ liquid cell has also been used in soft-X-ray spectroscopy microscopy to investigate the lithiation behavior of LiFePO₄. With this data we show that with the liquid-cell methods developed we can routinely perform in-situ characterization in TEM and X-ray microscopy.

Photo-electrochemical water splitting system is a promising way to produce solar fuels. In such a system, catalysts are needed to promote oxygen evolution reaction. Many metal oxides (such as IrO_x, RuO_x, and NiFeO_x) have shown catalytic activities for oxygen evolution reaction. Amound them, IrOx shows great stability and activity in acid conditions. Unfortunately, little is known about the mechanism and the structures of critical intermediates in these catalysts. Therefore, a fundamental understanding of the structures of critical intermediates is highly needed. To this end, we are going to characterize IrOx by various synchrotron X-ray spectroscopic techniques in the real working condition including electrochemical system and photo-electrochemical system. The techniques include X-ray absorption near edge spectroscopy (XANES), extended X-ray absorption fine structure (EXAFS), and ambient pressure X-ray photoelectron spectroscopy (APXPS). XANES can be used to provide information about the oxidation state of metal. EXAFS can provide information about the local coordination environment around the metal atom, such as coordination numbers and distances of ligands. APXPS could probe oxygenated surface species. These technologies allow us to study heterogeneous catalysts for artificial photosynthesis/solar fuels, chemical bonding and reactions on surfaces. These deeper fundamental understandings will lead us to create more active, selective, and robust catalysts based on earth abundant materials.

I will demonstrate how electron and x-ray spectroscopy can be used to address fundamental questions regarding the reaction mechanism and active sites of the Oxygen Reduction Reaction (ORR), Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER). We have developed in-situ XPS capabilities using a membrane assembly where either the anode or cathode side is exposed to a differential pumped environments where direct measurements of the changes in the catalyst and various reaction intermediates can be probed during ORR on Pt, OER on IrO₂ and HER conditions for MoS₂. We have also recently conducted high-energy resolution fluorescence detection (HERFD) studies of the Fe and Ni K-edges under OES conditions in the highly active Ni-Fi oxyhydroxides to determine the nature of the active sites. In particular we observe that Fe encounter an extremely strained local geometry when Ni undergoes a transformation from the 2+ to 3+ state.

Photoelectrochemical cells provide an alternative route to renewable storable energy production. The solid-liquid interface is crucial for the performance of the cells. Hitherto their operating principles have been inferred from combinations of experiments and models but simultaneous observation of the surface chemistry and the band energetics during operation is still required. We present the novel application of operando photoelectron spectroscopy in which electrochemical control is afforded during the course of the experiment. Using tender X-ray synchrotron radiation allows one to monitor the solid surface, the solid-electrolyte interface and the bulk electrolyte as a function of electrochemical potential. On metallized and semiconducting samples, ohmic and rectifying junction behavior was verified. Non-linear potential response of the core level positions demonstrates the influence of defect derived surface states on the Galvani potential across the complete cell.

Perovskite structure La doped barium stannate (BaSnO₃) has received interest for applications in energy including photocatalysts for solar fuels. Its high electron mobility of ~ 320 cm² V^-1 s^-1 may provide for more efficient separation of photogenerated electron-hole pairs in photo-electrochemical cells. The high electron mobility originates in part due to the predominantly Sn 5s character of the conduction band minimum (CBM) which yields a band mass ~ 0.2m_o as well as to the relatively high relative permittivity of ~ 20 which is large enough to provide screening of scattering centers. The simple Sn 5s structure of the CBM of La doped BaSnO₃ also makes it an intriguing system to study the effect of two dimensional charge confinement (2DEG) on thermoelectric and transport properties of oxides owing to the complex behavior of confined carriers in perovskite oxides where the conduction band manifold is derived from d orbitals such as SrTiO₃ [1]. To explore physics of 2DEGs at perovskite structure oxide interfaces and to develop perovskite structure oxide materials for applications in energy an understanding of interface electronic structure and band alignments at perovskite oxide heterointerfaces is vital.
In this study the interface formation between CaSnO₃, BaSnO₃, and SrTiO₃ is studied using x-ray and ultraviolet photoelectron spectroscopies with in-situ deposition of CaSnO₃ and La doped BaSnO₃ and SrTiO₃ thin films on 1 wt.% Nb doped SrTiO₃(001) (Nb:STO) substrates by pulsed laser epitaxy. Film structure was characterized using x-ray diffraction and Cs-corrected high angle annular dark #64257;eld scanning transmission electron microscopy. The valence band maximums of all three oxides are found to be close in energy < 0.2 eV in contrast to recent theory predictions [2]. Transitivity and commutativity is demonstrated through in-situ growth of SrTiO₃/BaSnO₃/CaSnO₃/Nb:STO and SrTiO₃/CaSnO₃/BaSnO₃/Nb:STO heterostructures. The in-situ photoemission studies will be compared to computational studies of the electronic structure and band alignment at the stannate-titanate interfaces using density functional theory and implications of the results in the context of stannate-titanate heterointerfaces for application in energy will be discussed.
[1] K. Kerman, S. Ramanathan, J. D. Baniecki, M. Ishii, Y. Kotaka, H. Aso, K. Kurihara, R. Schafranek, and A. Vailionis, Applied Physics Letters 103, 173904 (2013)
[2] L Bjaalie, B Himmmetoglu, L Weston, A. Janotti , and C G Van de Walle, New J. Phys. 16, 0225005 (2014)

The slow kinetics of the oxygen evolution reaction is one of the performance-limiting factors for hydrogen production in electrolyzers and photo-electrochemical cells. Establishing the fundamental relationships between structure and electrochemical activity on model single crystal oxides used for the oxygen evolution reaction could lead to future performance improvements [1]. Additionally, the atomic structure of complex epitaxial oxides can be manipulated through epitaxy when the layer is only a few unit cells thick and deposited on an appropriate substrate. Establishing the electronic properties of the interface then allows to determine the origin of activity enhancements. For instance, the band offsets between the catalytically active layer and the substrate determine the resistance associated with charge transfer across the layer/substrate interface. This affects the ultimate electrode efficiency which could be much lower compared to the one of the material in the bulk [2]. The band offsets at the interface between functional materials must thus be determined reliably.
In this work, we determined the band offsets between epitaxial LaCoO₃ single crystals grown by pulsed laser eptiaxy and SrTiO₃ (001). The offsets were determined by x-ray induced photoelectron spectroscopy performed without exposing the sample to atmospheric contamination. The offsets were determined for intrinsic and hole-doped LaCoO₃ via Sr²⁺ and Ca²⁺ doping. Large valence band offsets of 2.5 to 2.8 eV were obtained between the nominally undoped and hole-doped LaCoO₃ films and the SrTiO₃ (001) substrate, with the SrTiO₃ (001) valence band lying lower in energy. Implications of the results for fundamental studies of structure-electrochemical activity relations for the oxygen evolution reaction on model thin film epitaxial LaCoO₃ electrodes will be discussed.
QVO acknowledges the financial support of the F.R.S.-FNRS and the National Institute of Communications Technology for a Japan Trust award.
[1] S.H. Chang et al., Nat. Commun. 5 (2014) 4191.
[2] K.A. Stoerzinger et al., Energy Environ. Sci. 6 (2013) 1582.

Understanding and controlling the synthesis and assembly of low-dimensional, energy-efficient materials by design requires real-time monitoring and control of the growth environment, measurement of nucleation and growth kinetics, and remote characterization of materials properties. Here we describe recent progress on in situ laser spectroscopy and imaging techniques to understand and control the growth of nanomaterials on surfaces for functional applications - from ultrathin one- and few-layer 2D crystals of graphene and metal chalcogenides, to highly structured coatings of aligned nanotubes or mesoporous nanoparticle architectures. To characterize nucleation and growth kinetics, pulsed reactant delivery is employed to provide well-defined fluxes and arrival times. Laser-based techniques such as interferometry, absorbance, Raman scattering, and photoluminescence will be described that serve as remote optical probes to measure and control nanomaterial properties, and measure nucleation and growth kinetics for the development of growth models. Using pulsed CVD, growth of carbon nanotubes and graphene reveals distinct nucleation, growth, and termination regimes indicative of reactive intermediates. Similarly, during pulsed laser deposition from solid targets in background gases, ultrasmall nanoparticle ‘building blocks&’ that are formed either in the gas-phase enroute, or on the substrate surface, are revealed as intermediates that assemble to form unique hyperbranched mesoporous nanoparticle architectures, crystalline nanorods, and 2D nanosheets with interesting metastable phases. Temporally- and spatially-resolved gated-ICCD imaging, laser spectroscopy, and ion probes are employed as gas-phase in situ diagnostics to understand and control the plume expansion conditions in order to synthesize and deliver ultrasmall “amorphous” nanoparticles (UNPs < 3 nm) of oxides or metal chalcogenides as “building blocks” to explore the assembly of 1D, 2D, and 3D functional structures. HRTEM and EELS are used to characterize the particle composition and structure, and to study the mechanisms of oriented attachment and crystallization into novel phases via in situ annealing. The synthesis of novel phases and architectures of TiO₂, a workhorse wide-bandgap semiconductor, are described from UNP “building block” precursors. For metal chalcogenides, PLD of GaSe UNPs are described for formation of 2D nanosheets with high photoresponsivity. Using these UNP precursors, a new digital transfer growth technique was developed for the growth of large metal chalcogenide (GaSe) and dichalcogenide (MoSe₂) 2D crystals.
Research sponsored by the U.S. Dept. of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Div. (synthesis science) and Scientific User Facilities Div. (characterization science).

The limited understanding of mechanisms that mediate solid oxide fuel cell (SOFC) anode performance is due to a lack of experimental methods that can probe species and component materials directly during operation. While there have been extensive studies to investigate the efficiency of Ni-YSZ-based electrode materials in different reforming conditions, these have been performed using post-mortem and in situ electrochemical analyses with little insight on specific mechanisms that lead to fuel oxidation and cell degradation. A new integrated approach of near infrared thermal imaging (NIRTI), Raman spectroscopy, and Fourier-transform infrared emission spectroscopy (FTIRES) is utilized to correlate the chemistry of carbon formation with traditional electrochemical measurements for methane and simulated biogas fuels in operating SOFCs.
Plain, wet (steam), and dry (carbon dioxide) reforming conditions for methane are investigated on anode- and electrolyte-supported cells. NIRTI results demonstrate that cooling on the anode surface due to endothermic hydrocarbon cracking for dry reforming or simulated biogas is significantly greater than for unreformed methane on both types of cells. Raman and FTIRES both show that more carbon is deposited with methane than with biogas. The small amount of carbon formed is limited to lower temperatures with simulated biogas whereas carbon formation occurs to a great extent at all temperatures with methane. Exhaust gas analysis with ex situ FTIR absorption measurements and mass spectrometry are combined with in operando measurements to further characterize and quantify species involved in SOFC operation. These findings serve as benchmark data for a better understanding of mechanisms responsible for performance and degradation of SOFCs.

Grid- and transportation-level energy storage applications demand battery chemistries that are low-cost, safe, and have a long cycle life. Alkaline batteries that are based on a Zn-MnO₂ chemistry are able to meet the first two targets, as they can achieve high energy densities that are comparable to lithium-ion batteries (160-250 Wh/g) at a low cost (< $100/kWhr). However, the rechargeability of traditional Zn-MnO₂ alkaline cells is limited by irreversible phase transformations that occur in the MnO₂, particularly in the presence of Zn ions, during discharge.
In recent work, we have shown that Bi- and Ba-doping the MnO₂ cathode as well as optimizing the electrolyte chemistry can lead to vastly improved specific capacity and cycling lifetime figures (> 350 mAh/g for nearly 100 cycles, > 250 mAh/g for over 250 cycles). To gain insight into the mechanisms responsible for the improved performance, we extensively studied the structural changes that occur in doped-MnO₂ electrodes during cycling in various electrolytes using a range of experimental techniques, including in-situ Raman spectroscopy and in-situ impedance spectroscopy. Prior to cycling, the doped-MnO₂ electrodes are in the pyrolusite phase (β-MnO₂). When we begin to cycle the cells, however, our results shown that the electrode and electrolyte chemistry both have a significant influence on the structural evolution of MnO₂. For example, as observed with in-situ Raman spectroscopy, in an aqueous KOH electrolyte the electrode transforms into birnessite (δ-MnO₂), whereas when LiOH is also present in the electrolyte an Li_xMn_2-xO_4-x phase forms instead. Additionally, in-situ impedance spectroscopy analysis suggests that the increase in specific capacity during the initial break-in period (i.e., first 10-20 cycles) correlates with a decrease in both the charge-transfer resistance and Warburg impedance.
A deeper understanding of how electrode and electrolyte chemistries influence the underlying structural changes that occur during cycling will go a long way in enabling doped-MnO₂ electrodes to achieve thousands of cycles against Zn and other earth-abundant materials.

Interfacial charge transfer is ubiquitous to many chemical and physical processes and can occur on ultrafast time scales on the order of femtoseconds to picoseconds. Probing dynamics on such time scales necessitates the use of ultrafast laser spectroscopies, but obtaining information from real interfaces is notoriously difficult due to an overwhelming contribution from the bulk of either constituent. We have shown time resolved electric field induced second harmonic generation (TR-EFISH) is a valuable tool in elucidating charge transfer dynamics at buried interfaces [Science 328, 1543 (2010); Nat. Mater. 12, 66 (2013); J. Phys. Chem. C 117, 10974 (2013)] by taking advantage of the inherent symmetry breaking and the sensitivity of SHG to electric fields. Here we report the development of a femtosecond spectral interferometry technique for second harmonic generation (SHG) with time, energy, and phase resolution. In particular, quantitative information on SHG spectrum and phase provides unprecedented detail on how interfacial electric fields rise and decay due to charge transfer on the femtosecond time scale. Using the model system of organic/inorganic semiconductor interfaces, copper pthalocyanine/gallium arsenide CuPc/GaAs (001), we show the femtosecond dynamics of band renormalization, charge carrier motion, and interfacial charge transfer, all induced by across bandgap optical excitation of the one of the two semiconductors.

Electrochemical capacitors (ECs) are a vital component of today&’s electrochemical energy storage, having power and energy densities intermediate to batteries and electrolytic capacitors. ECs utilize porous carbon electrodes and store charge in the electrochemical double layer (EDL) formed at the electrode/electrolyte interface. The pore/ion size ratio will significantly affect the normalized capacitance and ion insertion kinetics, and it is essential to understand these relationships to optimize device performance.
Recently, in-situ Atomic Force Microscopy (AFM) was shown to be a valuable technique to monitor the volume changes experienced during charge/discharge. The volume changes are attributed to ion insertion into the carbon pores. The expansion/contraction of several porous carbon materials in combination with various electrolytes were examined with AFM. We will discuss possible strain mechanism and the influence of pore and ion size on ion insertion kinetics. We will focus on room temperature ionic liquids (RTILs) as electrolyte. RTILs are salts which are liquid at room temperature and exhibit unique properties, and as such have found a wide variety of applications over the past number of years, particularly in the field of electrochemistry.
While ion insertion into the porous electrodes is one vital component for capacitor performance, just as important is the formation of the double layer. We will present how AFM force spectroscopy can be used to visualize the EDL for RTILs at a model surface. Ion positions can be extracted from discontinuities in the force distance curves and are compared with predictions from molecular dynamics simulations. We will show that we can resolve molecules with different orientations and show how the ions re-order when the electrode is biased. We will highlight spatial variations of ion layering across the surface revealing 3D defect structures in the on layering.
This work was supported as part of the Fluid Interface Reactions, Structures and Transport (FIRST) Center, and Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Measurements were performed at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences.

We explore atomic level spatial variability of electronic structure in Fe-based superconductor FeTe0.55Se0.45 (Tc = 15 K) using current-imaging tunneling-spectroscopy (CITS). We then use multivariate statistical analysis, as well as more traditional Dyne&’s fitting techniques¹, to analyze the data and differentiate regions of dissimilar electronic behavior that can be identified with the segregation of chalcogen atoms, as well as boundaries between terminations and near neighbor interactions.
Multivariate and clustering analysis of the 3D (or higher) dimensional data set allows identification of the spatial localization of electronically dissimilar regions. However, the quality of the CITS experiment depends largely on the drift of the tip while the measurement is performed. Ideally, imaged areas and spectroscopy areas would be maximally correlated; e. g. the tip position on the spectroscopy grid can be mapped exactly on the STM image. This allows accurate identification of the source in the electronic signal which allows for chemical discrimination of the STM data including separation of atomic identities, proximity and local configuration effects.
We study the Fe_1+yTe_xSe_1-x superconducting surface via Low Temperature CITS in order to examine the superconducting gap of the surface to identify chalcogen separation areas and distinguish atoms on the surface. The CITS data is analyzed via multivariate statistical methods such as PCA ^2-5 k-means⁶ and Bayesian unmixing⁷ to extract areas or chalcogen separation and try and distinguish the chemical signature of Te and Se. Dyne&’s fitting results are also reassembled into spectral vectors and analyzed via the multivariate methods to compare gain additional insight into the chalcogen segregation.
1. W. Lin, Q. Li, B. C. Sales, S. Jesse, A. S. Sefat, S. V. Kalinin and M. Pan, ACS Nano 7 (3), 2634-2641 (2013).
2. S. V. Kalinin, B. J. Rodriguez, J. D. Budai, S. Jesse, A. N. Morozovska, A. A. Bokov and Z. G. Ye, Phys. Rev. B 81 (6), 064107 (2010).
3. S. Jesse and S. V. Kalinin, Nanotechnology 20 (8), 085714 (2009).
4. M. Bosman, M. Watanabe, D. T. L. Alexander and V. J. Keast, Ultramicroscopy 106 (11-12), 1024-1032 (2006).
5. N. Bonnet, edited by P. W. Hawkes (Elsevier Academic Press Inc, San Diego, 2000), Vol. 114, pp. 1-77.
6. S. S. Haykin, Neural networks: a comprehensive foundation. (Prentice Hall, 1999).
7. N. Dobigeon, S. Moussaoui, M. Coulon, J. Y. Tourneret and A. O. Hero, Signal Processing, IEEE Transactions on 57 (11), 4355-4368 (2009).

Electrochemical reactivity of solid surfaces underpins functionality of a broad spectrum of materials and devices ranging from energy storage and conversion, to sensors and catalytic devices. The surface electrochemistry is however a complex process, controlled by the interplay of charge generation, field-controlled and diffusion-controlled transport. In order to understand the fundamental mechanisms underpinning electrochemical functionality, it is vital to separate the spatial localization of reaction and transport processes.
Here we explore the conductivity mechanisms of nanostructured ceria (NC), using the synergy of nanofabricated devices and time-resolved Kelvin Probe Force Microscopy (tr-KPFM), an approach we refer to as energy discovery platform. While NC is extensively used as a mixed ionic-electronic conductor (MIEC) in solid oxide fuel cells and gas sensors, the origin of its conductive behavior is still controversial: anisotropic bulk conduction, as well as proton-based conduction - facilitated by surface water adsorption - have been previously reported as contributing to the MIEC behavior in NC.
To prepare the nanofabricated device, NC was prepared by Chemical Solution Deposition (CSD) and Physical Vapor Deposition (PVD) on Si/Si3N4 and quartz substrates. Cr/Pt stripes, serving dual function of catalytic sites and current collectors, were created on top of ceria by lift-off and sputtering. Through tr-KPFM, the surface potential and current mapping in both the space and time domains is obtained, enabling analysis of local ionic and electronic transport and their dynamic behavior on the 10 ms to 10 s scale. Based on their different responses in the time domain, conduction mechanisms can be separated and identified at a variety of environmental conditions, such as humidity and temperature. Generally, higher temperature and/or relative humidity led to stronger polarization and relaxation behavior in response to stimuli of equal strength. At temperatures le;125°C, the detected surface potential change over time is mainly a result of transport of protons and hydroxyl groups. Surface defects and triple phase boundary (TPB) serve as active sites for electrochemical reactions (charge injection, etc.) and thus they play a crucial role in surface conductivity of NC. The theoretical modeling of ion transport through finite element method allows for creation of a minimal model consistent with observed phenomena, and establishing of the dynamic characteristics of the process, including mobility and diffusivity of charge species.

The manganese oxides (manganites) are increasingly being used as cathodes in solid oxide fuel cells [1], necessitating understanding of surface oxygen dynamics [2,3] in these complex oxides. Yet, the properties at the surface of the manganites are poorly understood, mostly due to difficulties in sample preparation. Here, we use in-situ techniques to grow epitaxial La_1-xCa_xMnO₃ (LCMO) films by pulsed laser deposition, and study the surface properties through Scanning Tunneling Microscopy (STM) and conductive atomic-force microscopy (c-AFM) in ultra-high vacuum. Tip-based modification experiments prove the ability to deterministically create oxygen vacancies on the surface, as well as deposit atomic units or clusters, while I-V curves suggest local metallicity that is not observed in the bulk. The metallic conductance is also observed in c-AFM scans and point I-V spectroscopy with the conductive AFM tip. These studies show the potential for tuning the surface properties of manganites by scanning probe methods, and further highlight the unique surface states that appear in the manganese oxides.
This research was sponsored by the Division of Materials Sciences and Engineering, BES, DOE (RKV, AT, AG, PM, SVK). This research was conducted at and partially supported by (AB) the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. AG acknowledges fellowship support from the UT/ORNL Bredesen Center for Interdisciplinary Research and Graduate Education.
References
1. C. Sun, R. Hui, J. Roller, Cathode materials for solid oxide fuel cells: a review. J Solid State Electrochem14, 1125 (2010).
2. B. Stöger, M. Hieckel, F. Mittendorfer, Z. Wang, D. Fobes, J. Peng, Z. Mao, M. Schmid, J. Redinger, U. Diebold, Phys. Rev. Lett.113, 116101 (2014).
3. B. Bryant, C. Renner, Y. Tokunaga, Y. Tokura, G. Aeppli, Nat. Comm.2, 212 (2011).

The 4.7V LiMn_1.5Ni_0.5O₄ spinel is an attractive candidate for high voltage lithium ion positive electrodes. The emerging interest in Na⁺ ion batteries has increased the relative importance of higher voltage positive electrodes, as the Na+ at the negative electrode induces a lower output voltage. The electrochemical and structural characteristics of higher voltage Na_xMn_1.5Ni_0.5O₄ relative to Na_xMn₂O₄ during ion insertion are investigated for the first time. High-resolution electrochemistry, coupled with in-situ and ex-situ X-Ray diffraction reveal a reversible topotactic insertion of Na⁺ ion into the spinel structure with near theoretical utilization. Distinct electrochemical challenges brought fourth by Na⁺ ion insertion into the spinel structure is discussed in detail.

We combine in situ atomic force microscopy and in situ real-time X-ray scattering to investigate molecular nucleation and growth processes in organic-inorganic semiconductor hybrids that are promising candidates for optoelectronic applications. In our study conducted at ID03 at the European synchrotron radiation facility (ESRF) we monitor the X-ray reflectivity in real time in a broad q_z range during thin-film growth and deduce details about the 3D / 2D growth mode as well as the crystal phase content.
We show that through the terminal fluorination of para-sexiphenyl (6P) it is possible to significantly improve the growth mode by preventing a contamination with a second crystal phase as found for 6P, and further the fluorinated molecule exhibits smooth layer-by-layer growth. This improved growth mode is a result of enhanced molecular diffusivity and a lower Ehrlich-Schwoebel barrier leading to increased interlayer mass transport.
Our results demonstrate that selective chemical tuning of functional organic molecules presents a viable strategy to design crystalline organic layers with thin-film morphologies and phase purity as demanded for well-defined interfaces in efficient light emitting devices and solar cells.
Reference:
M. Sparenberg*, A. Zykov*, P. Beyer, L. Pithan, C. Weber, Y. Garmshausen, F. Carlagrave;, S. Hecht, S. Blumstengel, F. Henneberger, S. Kowarik. Controlling the growth mode of para-sexiphenyl (6P) on ZnO by partial fluorination. Accepted for publication in Phys. Chem. Chem. Phys. (2014)

Oxide materials are known to be active in a variety of redox reactions, making them important for many energy technologies. Unfortunately, the complex interactions between such reactions and the structural/chemical evolution of the oxide surface are not well understood. This has hindered progress in many areas, including solid oxide fuel cells, corrosion, and the development of new heterogeneous catalysts. With the advent of high precision growth techniques, epitaxial oxide heterostructures can now be synthesized with controlled strain, orientation, and surface termination. When combined with the unique capabilities of the APS, this permits in situ studies of redox reactions on model oxide surfaces and can therefore lead to the development of much needed structure-reactivity relationships for this important class of materials.
In this presentation, I will discuss recent in situ x-ray results on epitaxial SrCoO_x films and their behavior during oxidation and CO oxidation, as well as epitaxial SrRuO₃ films and their behavior during the oxygen evolution reaction. We find significant structural changes during reaction as well as a large dependence of reaction rates on crystal orientation.

Synchrotron-based high-energy X-ray Compton scattering has been developed as a unique tool to characterize energy materials under in-situ conditions. The advantages of this technique are high penetration power into objects and high sensitivity to orbital occupancy. By making the most of the advantages, it will pave the way for quantum electrochemical analyses of energy storage materials and products under in-situ conditions. Here we present recent studies on a commercial battery and a series of spinel lithium manganite as positive electrode materials, employing the line-shape analysis of Compton scattered X-rays. The X-ray Compton scattering experiments have been performed with incident 115 keV X-rays at the BL08W beamline, SPring-8, Japan.
The study on a commercial battery includes the in-situ and operando observation of a working coin cell (CR2032) with positive MnO₂ and negative Li electrodes. Scanning the collimated X-ray beams throughout the cell, Compton scattered X-rays from a probing volume have been measured as a function of one-dimensional position and discharge time. The line-shape analysis, as well as the intensity analysis, of Compton scattered X-rays, has succeeded in visualizing the structural and electrochemical evolutions in the discharging coin cell.
The study on spinel lithium manganite is the high-resolution line-shape analyses of spinel Li_xMn₂O₄ with 0 < x < 2, together with first-principles band structure calculations. Comparisons between the experiment and theory show that the active orbital involved in lithium insertion and extraction process is mainly the oxygen 2p orbital, although the manganese 3d states undergo spatial delocalization involving 0.16 electron per manganese site during the battery operation. This quantum mechanical approach paves the way for an advanced characterization of lithium ion batteries, in which the redox orbital becomes the focus of materials design and engineering.
The above demonstrations are critical steps for developing an in-situ method of quantum electrochemical analyses on large batteries such as those mounted on electric vehicles.
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This work is supported by the Development of Systems and Technology for Advanced Measurement and Analysis program under Japan Science and Technology Agency.

Real-time and in situ X-ray scattering is well suited to study the complex growth kinetics of molecular semiconductors. Here we investigate the structural order and morphology of the prototypical organic semiconductor C₆₀, which is crucial for the performance of many organic devices such as e.g. solar cells. By the unique combination of time resolved diffuse and specular X-ray scattering methods at PETRA III (DESY) and kinetic Monte-Carlo simulations (KMC) we are able to quantify the physical nucleation and growth processes of C₆₀ on C₆₀.
Exploiting the high dynamic range of advanced pixel detectors, we are able to acquire both weak diffuse scattering (in GISAXS geometry) and, at the same time, strong specular growth oscillations at the anti-Bragg position (that is at half the q value of the Bragg reflection). From the anti-Bragg growth oscillations we determine the layer coverages during the vertical film growth. From the simultaneously measured 2D diffuse x-ray scattering pattern we extract the island density and island diameter as a function of temperature, deposition rate and film thickness. We compare this experimental data on island formation and successive layer filling with kinetic Monte Carlo simulation of the growth process, and from this are able to determine the diffusion energy (0.54eV), step-edge barrier (0.11 eV) and binding energy (0.13 eV). This experiment and theoretical model represents a first example of a molecular system whose growth can be modelled in the multilayer regime, enabling predictive simulations and a detailed understanding of C₆₀ growth.
“Unravelling the multilayer growth of the fullerene C60 in real time”
S. Bommel, N. Kleppmann, C. Weber, H. Spranger, P. Schaefer, J. Novak, S.V. Roth, F. Schreiber, S.H.L. Klapp, S. Kowarik
Nature Communications, accepted

Bismuth sodium titanate (BNT) is a chemically disordered, lead-free piezoelectric. Doping with barium leads to instabilities that induce structural phase transitions and thereby modify the piezoelectric behavior. We used several in situ x-ray and neutron scattering techniques to determine the influence of Ba-doping on chemical disorder, structural disorder [1] and lattice dynamics. A model will be presented that tries to unify all results in a coherent picture.
[1] John E. Daniels, , Wook Jo, Jürgen Rödel, Daniel Rytz, Wolfgang Donner
Applied Physics Letters, 98, (2011), 252904

The synthesis and use of materials for energy related applications requires the control of complicated metastable states and transitions between metastable states. While metastable processes are often understood on a phenomenological level through indirect and ex-situ measurements, many of the underlying mechanisms are still not known. In situ x-ray techniques have allowed us to study average properties of the dynamic processes in real materials, under real conditions in real time. In this talk, I will present results from our research programs at the Advanced Photon Source (APS) that examine the growth of thin films and ionic processes in complex oxides. In particular, I will present results from recent experiments that examine homoepitaxial growth of GaN, and the dynamic response of La_1-xSr_xCo_1-yFe_yO₃ (a fuel cell cathode material) thin films to changes in oxygen partial pressure and applied voltage. While these in situ x-ray measurements have helped quantify microscopic dynamic processes, the continued development of x-ray sources is enabling a new generation of spatially resolved x-ray techniques including coherent diffraction imaging. I will discuss how new x-ray techniques will allow the measurement of materials processes around isolated features and as individual events (not just as statistical averages) in order to understand and control dynamic processes in materials.

Grid-level energy storage demands low-cost, safe, reliable battery chemistry. One technology which satisfies these requirements is the Zn-MnO2 alkaline battery chemistry. This battery type has high energy density (comparable to that of a Li-ion battery), low cost per kilowatt-hour, and is relatively safe. However, their rechargeability is limited by phase transformations which occur in the MnO2 cathode during discharge by more than one electron, which transform it into an spinel phase which is generally considered to be electrochemically inert. As a result, depth of discharge is generally limited to no more than 50% of the cells 1-electron capacity. We have studied this phase transformation and the failure modes of alkaline batteries using synchrotron-based energy dispersive X-ray diffraction (EDXRD) techniques. Using EDXRD, we directly observed the phase transformation occurring in the cathode as function of rate and time in real time for a range of different discharge rates. We see that previous estimations of the phases evolved during cycling are partially supported. Our observations also suggest that the transformed material is not in fact electrochemically inert, and that the phase transformation which occurs in the cathode may be reversible. This suggests that Zn-MnO2 rechargeable batteries can possess sufficient energy density to enable economical grid-scale energy storage and potentially even power electric vehicles.

Understanding the physical evolution of the constituents of a battery during discharge can offer detailed information about state of charge as well as failure mechanisms. However, typical methods of characterizing the internal components of batteries are often only applicable post mortem. Our previous work has used energy-dispersive x-ray diffraction (EDXRD) spectroscopy to image discrete volumes within Zn-MnO2 “alkaline” batteries, and has shown the evolution of the internal components during discharge. Most notably, the oxidation of the anode from Zn to ZnO has been quantified as a function of state of charge. We have also shown that dynamic testing of LR6 alkaline batteries (AA) in the form of a simple bounce test can interrogate morphological evolution within the battery (Bhadra, et al.) through determination of the coefficient of restitution. Building from this work, we present an in-operando technique through which the components of a AA cell can be determined. Our structural results agreed well with the results presented in our previous bounce tests and EDXRD studies, which was that densification of the anode occurs at 50% depth of discharge, well before full discharge.

Lithium-ion batteries (LIBs) using germanium as the anode material are drawing more attention recently, due to its higher lithium-ion diffusivity and electrical conductivity relative to silicon. However, there is still limited understanding of the reaction mechanisms governing crystalline Ge and the effects of cycling rate on its transformations into various amorphous and crystalline phases during the electrochemical charge and discharge process. In this work, we carry out operando X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) studies of Ge anodes in carbonate-based electrolyte. These two probes measure both crystalline (from XRD) and amorphous (from XAS) phase transformations with time, which allows detailed information on the Ge anode to be obtained. We find that Ge electrodes using carbon nanotubes as conductive additives exhibit higher structural (from XAS) and electrochemical reversibility compared to the case for carbon black additives, giving rise to better stability in subsequent cycling. In addition, the formation of crystalline Li₁₅Ge₄ during lithiation is suppressed beyond a certain critical cycling rate. The impact of the formation of crystalline Li₁₅Ge₄ on the reversibility and lithium storage capabilities of Ge electrodes will be discussed. Both our operando XRD and XAS results present new insights into the reaction mechanism of Ge as anodes in LIBs, and correlate phase transformation and local structural changes with electrochemical cycling and lithium storage properties.

Atomic layer and metal organic chemical vapor deposition (ALD and MOCVD) are both important and highly versatile growth techniques for a variety of thin film energy materials. ALD is unmatched in its ability to produce conformal films, and MOCVD is the industry standard for producing stoichiometric compounds over large areas. A key consideration in many modern devices is the atomic structure of the heterointerface, which often ultimately governs the electronic or chemical process of interest, whether it concerns, e.g., photovoltaic conversion efficiency or catalytic activity. The structure of the deposit and its interface naturally depends on the atomic mechanisms that take place during growth, which for ALD and MOCVD, have been difficult to study due to the near-atmospheric pressure, and for MOCVD, high temperature deposition conditions. In LMGP laboratory we optimize and use ZnO thin films and nanostructures (nanowires, nanoparticles) as building blocks for micro-electronics, optoelectronics and photovoltaic devices. We aim to understand the growth and doping mechanisms of ZnO nanostructures grown by chemical deposition techniques [1], including ALD and MOCVD. In this presentation, we will demonstrate that the combination of in situ characterization techniques, i.e., synchrotron x-ray scattering [2] and optical substrate curvature measurements, is a powerful approach with unique potential for obtaining real-time structural and chemical information during ALD [3] and MOCVD of ZnO on a variety of substrates. We have constructed a ALD/MOCVD chamber that mounts onto the heavy duty diffractometer at the beamline SIRIUS of SOLEIL Synchrotron (St Aubin, France). ZnO films were grown on either (001) oriented α-Al₂O₃ or Si substrates under different conditions. Through in situ observations of specular reflectivity and grazing-incidence diffraction, we monitored changes in film thickness, roughness, stress, layer density, and composition in real time, starting with the initial monolayer of growth. We find that the growth behavior and crystalline texture depends strongly on the choice of substrate. Preliminary theoretical results on the effects of surface chemistry on initial growth characteristics will also be discussed.
[1] V. Consonni, E. Sarigiannidou, E. Appert, A. Bocheux, S. Guillemin, F. Donatini, I.C. Robin, J. Kioseoglou, F. Robaut, ACS Nano 8, 4761 (2014)
[2] D.D. Fong, C. Thompson, Annu. Rev. Mater. Res. 36 (2006) 431. D.D. Fong, C.A. Lucas, M.-I. Richard, and M.F. Toney, MRS Bulletin, 35, 504., (2010)
[3] D. D. Fong, J. A. Eastman, S. K. Kim, T. T. Fister, M. J. Highland, P. M. Baldo, and P. H. Fuoss. Appl. Phys. Lett.97, 191904 (2010)

Solid oxide fuel cells (SOFCs) are an efficient, combustion-less, pollution-free power source, and are promising for both stationary and mobile applications (auxiliary power sources). Currently a cermet consisting of yttria stabilized zirconia (YSZ) and Ni is used as the anode material but the cost of high-temperature materials and the degradation associated with high operating temperatures (>1000 °C) are two major roadblocks preventing their widespread applications. Both the cost and materials problems may be mitigated by using ceria doped with Pr (PDC) and/or Gd (GDC) and Ni cermets. We have employed in situ electron energy-loss spectroscopy (EELS) to measure the nanoscale redox activity of PDC, Ni-loaded PDC and Ni-GDC cermet using an environmental electron scanning transmission electron microscope (ESTEM). HREM images and EELS data were collected in the temperature range of 500 °C to 800 °C in 130 Pa of hydrogen atmosphere. We will present experimental results and theoretical models used to elucidate the effect of compositional heterogeneity, particle size and Ni catalyst on nanoscale redox properties of PDC and GDC. Additionally we will discuss the impact of correlative techniques, such as Raman spectroscopy and ESTEM, on the in-depth understanding of redox reactions.

The high demand for new energy storage materials has created a need for experimental techniques that can provide real-time information on the dynamic structural changes/processes that occur locally at the electrode/electrolyte interface during battery operation. In this regard, in-situ electrochemical stages for (scanning) transmission electron microscopes ((S)TEM) enable the fabrication of a real “nano-battery” to study the fundamentals of electrochemical processes under operando conditions with the high spatial and temporal resolution of an electron microscope. Here, we describe quantitative operando observations using an in-situ liquid electrochemical (S)TEM cell to study lithium dendrite formation in rechargeable Li-ion batteries (results were obtained from a range of electrode/electrolyte combinations including a Pt microelectrode and LiPF₆ in PC electrolyte). Images in the STEM usually have mass thickness contrast, meaning that something thicker, heavier/more dense appears darker in the bright field image and lighter in the dark field image. As Li metal is lighter and less dense than the surrounding electrolyte, the formation of dendrites appears to be light in the bright field image and dark in the dark field image - the contrast is effectively “reversed”. Such contrast is unique to Li metal and provides a very straightforward way to identify Li metal (and therefore dendrites) during the nano-battery operation in the microscope. From the individual STEM images (that are combined to form video rate movie of the dynamic process), the amount of Li deposited/incorporated into the electrode during the charge/discharge cycle can be directly quantified and correlated with the standard ex-situ bulk scale cyclic voltammetry measurements, thereby providing a direct nanoscale view of the whole electrochemical process. Results show that the amount/morphology of Li dendrite changes after the first cycle due to the differences in initial surface area of the bare Pt electrode and the surface roughness of Pt electrode after Li dendrite deposition in subsequent cycles. This enables a direct link between the STEM images and the electrochemical behavior that can be extended to any combination of real battery systems (Na, Mg, Zn, Al etc. in aqueous or organic solvent) to provide significant insights into the electrochemistry of battery systems on the nanometer scale.
This work was supported as part of the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the US Department of Energy, Office of Science, and Basic Energy Sciences. The research is also part of the Chemical Imaging Initiative at Pacific Northwest National Laboratory under Contract DE-AC05-76RL01830 operated for DOE by Battelle. A portion of the research was performed using EMSL, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.

In situ environmental transmission electron microscopy (ETEM) is a powerful tool for investigating the fundamental science of energy-related catalytic nanomaterials since the atomic-level structural evolution can be observed while the material is exposed to reaction or near-reaction conditions. Specifically, we would like to apply this technique to the study of photocatalyst systems, a potential way to produce clean H₂ fuel from sunlight and water. To tackle that issue, an illumination system must be coupled with an ETEM to expose the sample to high intensity light.
An in situ illumination system has been developed previously for an FEI Tecnai F20 ETEM [1]. Using this system, we have observed detailed structural evolution on TiO₂ photocatalysts during exposure to in situ light and gas environments [2]. The same concept will be applied to an aberration corrected ETEM, the FEI Titan, which has been recently installed at Arizona State University and has an image corrector providing sub-Angstrom resolution. An optical fiber will be utilized to guide light into the TEM and onto the sample using the objective aperture port. The advantage of this design concept is that TEM hot stages can still be employed for in situ thermal processing of catalysts. This is critical for many fundamental studies on catalytic materials because thermal oxidizing or reducing treatments are often essential to create well defined initial reference states of the material. An LDLS EQ-99, laser driven xenon plasma source developed by Energetiq, will be employed to provide illumination over the wavelength range 200 - 800 nm. With such a light source, we should be able to achieve close to 10 suns intensity across the entire wavelength range making the system ideal for solar fuel work.
It is believed the combination of the superior resolution of this ETEM with the capability of in situ illumination will provide a deeper understanding on the photocatalyst behaviors. The issues associated with the design and fabrication of the fiber handling system will be discussed.
[1] B.K. Miller, P.A. Crozier, Microsc. Microanal. 19 (2013) 461-469
[2] L. Zhang, B.K. Miller, P.A. Crozier, Nano Lett. 13 (2) (2013) 679-684
[3] The support from US Department of Energy (DE-SC0004954) and the use of TEM at John M. Cowley Center for High Resolution Microscopy at Arizona State University is gratefully acknowledged.

Self-assembly of small objects such as molecules and nanoparticles (NP) into meso-structures is a very popular bottom-up construction method in material science and chemistry. It attracts scientists&’ much attention for its application in the fabrication of hybrid systems with multiple properties from different materials. The different types of interactions which drive the self-assembly of individual NPs has been depicted theoretically[1] and the self-assembly process of charged Au nanoparticles has been visualized by in-situ TEM[2]. Here, we further use the in-situ liquid TEM technique to study the self-assembly of Au nanoparticles under biased/current flow conditions in liquid environment. We modified the liquid cell first by deposition of a thin gold layer as electrodes. Which allow us to apply voltage to the liquid cell. Once there is liquid suspension with CTA+ coated Au nanoparticles (this means the Au nanoparticles are positively charged) across between the electrodes, there can be current flow through the liquid area. At non-biased condition, we use the electron beam with beam intensity lower than the threshold to trigger the nanoparticle movement[2]. Under this condition, all the particles are steady. Then the different biased voltage was applied to nanoparticle suspension. It was found that the nanoparticles movement took place. By statistics, we found the nanoparticle displacement is roughly the same under different biased voltage from 0V to 3V. But the number of moving nanoparticles is increasing along with the higher biased voltage/bigger current flow.
1. Bishop, K.J.M., C.E. Wilmer, S. Soh, and B.A. Grzybowski, Nanoscale Forces and Their Uses in Self-Assembly. Small, 2009. 5(14): p. 1600-1630.
2. Liu, Y., X.-M. Lin, Y. Sun, and T. Rajh, In Situ Visualization of Self-Assembly of Charged Gold Nanoparticles. Journal of the American Chemical Society, 2013. 135(10): p. 3764-3767.
This work was performed at the Center for Nanoscale Materials, a U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences User Facility under Contract No. DE-AC02-06CH11357.

Layer-structured materials with van der Waals gaps have long been utilized as active electrode materials in rechargeable Li ion batteries. However, understanding of their nanostructure and associated property changes during the charging/discharging process is lacking. We developed a novel planar micro-battery platform that allows us to measure in situ electrical transport and optical properties of two-dimensional (2D) molybdenum disulfide (MoS₂) at the level of individual crystallites a few microns in extent along the basal plane and a few nanometers in thickness. We observe a large conductivity increase of lithiated thick MoS₂ crystallites due to the formation of a percolative Mo nanoparticle network embedded in Li₂S matrix, which is confirmed by in situ transmission electron microscopy. The nanoscale study led us to develop a novel charging strategy for Li-ion batteries that largely improves the capacity and cycling performance confirmed in bulk MoS₂/Li coin cells. The proposed methodology can be generally applied to study a range of 2D electrochemical materials at the nanoscale.

Transition metal oxides (TMOs) have attracted attention for solid oxide fuel cell, gas sensor and catalytic applications, because of their ability to sustain ionic currents and varying degrees of oxygen deficiency.¹ For oxygen deficient perovskites of general composition AnBnO_3n-1 multiple vacancy ordered structures have been reported. These structures have multiple similarities, for example oxygen vacancies often form channels in [100]c, [110]c or both of these directions. Brownmillerite, one of the more common oxygen deficient structures, follows the stacking sequence -AO-BO₂-AO-BO-AO- with alternating octahedral and tetrahedral BO_x layers (OTOT), unlike the parent perovskite structure with all octahedral layers. It is also known that in many ionic oxides molar volume is linearly dependent on the overall oxygen stoichiometry of the material. However, the mechanism of oxygen ion motion at the atomic scale, which involves transitions via metastable and highly localized states, has not been sufficiently studied experimentally.
In this study, we have investigated the local oxygen vacancy ordering in LaCoO_3-x (LCO) thin films with atomic resolution by scanning transmission electron microscopy (STEM). In the as-grown state films were found to contain a substantial amount of disordered vacancies. The vacancy ordering and additional vacancy injection can be quickly induced by electron beam exposure, such that the LCO film goes through a series of phase transformations, starting from disordered perovskite LaCoO_3-x and ending with brownmillerite La₂Co₂O_5. Specifically, we directly observe the nucleation of tetrahedral layers in the perovskite matrix and their sequential transformation into 4:1 (OOOOT), 2:1 (OOT), and finally 1:1(OTOT) brownmillerite; these transitions require vacancy motion along both lateral and vertical direction. Tracing the path of the oxygen anions during this topotactic reduction process can help us understand the energy barriers and routes involved in ionic conduction. In the course of in situ experiments we observe multiple metastable configurations. We use experimentally observed transitional states as the input for DFT calculations in order to determine the energetically favorable ion trajectories in LaCoO₃ and evaluate the associated energy barriers. The information obtained from our studies can shed light on kinetics of the V_o motion, dynamics of oxygen reduction reaction, as well as contribute to fundamental understanding of oxygen transport at the atomic scale.
* Research supported by the U.S. Department of Energy, Basic Energy Sciences, Division of Materials Sciences and Engineering, and through a user project supported by ORNL&’s Center for Nanophase Materials Sciences , which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. DOE.
References
[1] A. Chroneos et al., Energy Environ. Sci. 4, 2774 (2011)
[2] Ole H. Hansten et al., J. Mater. Chem. 8(9) 2081 (1998)

We investigate p-i-n transducers as alternative devices for direct beta (β) -electron energy conversion to electrical current. Traditionally, β-electron conversion to electrical current is done via p-n junction semiconductor transducers which yield very low conversion efficiencies. This is mostly due to mismatch in length scales over which the β-electrons penetrate the transducers to generate electron-hole pairs, which is significantly larger than the depletion region size in the transducer responsible for their conversion into electric current. In p-i-n devices the depletion region size is extended by the presence of the intrinsic layer which ensures better electron-hole capture yield. We perform a systematic study using silicon based p-i-n devices inside a scanning electron microscope where the electron gun simulates β-electron emission with energies as high as 30 keV. Combinations of incident β-electron energy and intrinsic layer thickness are varied to determine the optimal conditions that yield the highest conversion efficiency and power output. Our experimental setup gives a platform for transducer testing that avoids the handling of radioisotopes until the devices are fully optimized and ready to be combined with an appropriate β-electron source for power generation.

Electrochemical systems are prime candidates to address the need for efficient, sustainable, safe, and cost-effective technologies for renewable energy conversion and storage. The essential physical phenomenon that occurs in all electrochemical energy systems is charge transfer across interfaces of different phases, or interphases. This transfer of charge is often accompanied by profound changes in microstructure, morphology, and composition at these interphases. The aim of in situ characterization methods is to capture the physical and/or chemical changes during charge transfer and thus provide a mechanistic understanding of their operation, limitations/failure modes, and opportunities for improvement. In my talk I will discuss several specific examples where microstructure imaging methods based on scanning electron microscopy, transmission electron microscopy and optical microscopy are combined with electrochemical characterization of Li ion batteries and photoelectrochemical hydrogen evolution cells to capture interfacial reactions and phase transformations in real time during device operation.

We use high angle annular dark field (HAADF) imaging and in situ quantitative electrochemistry to directly visualize growth kinetics of the solid electrolyte interphase (SEI) and Li electrodeposites on various electrode materials. We will briefly discuss the small-scale microfluidic electrochemical liquid cell platform used within the scanning transmission microscope (STEM). In this work, HAADF STEM imaging was used to facilitate Z-contrast conditions, which allows for quantitative image analysis, to estimate thickness and density of the SEI layer and Li deposits. It also allows for providing definitive proof of Li electrodeposition though contrast analysis. The dynamics of the SEI in response to the change in electric field is directly imaged; the SEI swells and becomes denser with each potential cycle. The nature of the electrode material is also discussed, specifically how the electrode&’s propensity toward electrocatalysis affects SEI growth and morphology.
Experimental work was supported by the Fluid Interface Reactions Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the Department of Energy&’s Office of Basic Energy Sciences Division (RLS, NJD and RRU). Additional personel support for experimental work was provided by the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy (RRU and KLM).

We will discuss the opportunities of using in situ liquid phase TEM to study the dynamics of Au nanoparticle assemblies. In one example, we track the motions of Au nanoparticles and quantify the spatial map of nanoscale inter-particle interactions from a statistically significant data set. There we are able to engineer the site-selective assemblies of Au nanoparticles, which is important for applications in plasmonics. In another example, Au nanoparticles are used to label biomolecules, and the dynamics as well as spatial arrangements of these nanoparticles give the 3D contour shape of biomolecules in their native environment.

Nano-scale engineering of rutile TiO₂, a promising material for use in the lithium ion battery, has drastically improved its specific capacity for Li exchange, capacity retention, and cycleability. However, an understanding of how the nanostructures change during lithiation is still lacking. Here, we present the first experimental proof that two phase changes occur during the lithiation of rutile TiO₂ nanostructures, derived from our investigation of real-time lithiation, performed on a single-crystal rutile TiO₂ nanowire, functioning as the anode of a solid prototype of a Li-ion battery inside a transmission electron microscope. From these results, it appears that the functional form of nanostructured titania actually has a monoclinic structure, which is stable over a relatively wide range of Li-ion loading.

Lithium-sulfur batteries are attractive for the future development due to their high theoretical specific capacity (1600 mAh/g), high energy density (2600 Wh/Kg), low cost and nontoxicity. However, the challenges involve a short cycling life of the batteries. So far, it lacks the fundamental understanding of the chemical processes during cycling. One of the key questions is whether Li₂S₂ phase exists and contributes to the lower practical cell capacity and poor rate behavior. Li₂S₂ was reported as stable specie in some work; but has not been confirmed experimentally. Here, we report real time imaging of polysulfide growth and dissolution during discharge and charge process in a nanofabricated liquid cell nanobattery using transmission electron microscopy (TEM). Two formation pathways of Li₂S have been identified, Li₂S could direct deposited on electrode surface or form Li₂S₂ first and then transform to Li₂S. During the growth, we observed the shape and structure changes of formed solid polysulfide, which result from the transformation of Li₂S₂ to Li₂S. Round shaped Li₂S₂ is formed firstly and it collapses in few seconds, while Li₂S nucleates and grows to rod shape. The select area diffraction of round particles suggests the Li₂S₂ have a hexagonal symmetry. Our in situ X-ray absorption experiments also indicate the formation Li₂S₂ during discharge process. These findings shed light onto Li/S batteries charge and discharge mechanisms and advancement in the future design of Li/S batteries.
The in situ TEM experiments were performed at Materials Science Division of Lawrence Berkeley National Laboratory (LBNL), which is supported by the U.S. Department of Energy (DOE) under Contract No. DE-AC02-05CH11231. HZ thanks the funding support from U.S. DOE Office of Science Early Career Research Program.