Electrochemical energy storage devices show a very pronounced interaction between electrode materials and electrolyte. Therefore, fatigue and ageing of Li-ion batteries can only be understood if the underlying changes in the materials are studied under real operation conditions inside a fully working battery. This requires non-destructive probes which can penetrate the housing, but nevertheless provide information about the details of the active materials inside the complete device. Neutron and high-energetic synchrotron radiation are ideal probes to reveal structural changes of the anode and cathode materials of Li-ion batteries over many charge-discharge cycles. Both radiations are essentially complementary: synchrotron radiation allows much faster data collection with a better time and spatial resolution and is more sensitive to heavier elements, while neutrons are most sensitive to light elements (especially H, Li, C, and O), which play the major role in light-weight energy storage. A combination of diffraction and tomography allows to follow changes in the materials during cycling and with proceeding fatigue.
Selected examples are shown, mainly for commercial 18650-type Li-ion batteries [1]. Neutron diffraction data allow a sophisticated analysis of the crystal structures and microstructures of the Li-intercalated graphite anode and of the Li-extracted layered transition metal oxides, like LiCoO2 or Li(Ni,Co,Mn)O2 (NCM). Rietveld refinement enables very reliable conclusions about the Li-distribution in the crystalline materials and a correlation with the states of charge (SOC) and health (SOH) [2]. The Li-occupation in the cathode material was compared in the charged and discharged state for up to 1000 cycles and revealed a reduced amount of exchanged "mobile" lithium within the fixed voltage window in excellent agreement with the observed capacity loss. The ratio between LiC6 and LiC12 in the fully charged state is also consistent with the observed degree of fatigue. Tomography gives an insight into changes in the interior cell geometry and electrolyte distribution. These results are combined with complementary post-mortem analysis and discussed in the light of fatigue and life time in dependence on the conditions of operation.
[1] A. Senyshyn et al., J. Power Sources 203 (2012) 126- 129.
[2] O. Dolotko et al., J. Electrochem. Soc. 159 (2012) A2082-A2088.

This presentation will be about some novel approaches on how to investigate energy materials, components and devices with x-rays and neutrons while they are under operation conditions.
For the lithium batteries I show a simple in-situ cell with which we did some hard x-ray XANES, EXAFS, resonant XRD and even resonant small angle scattering (ASAXS) during charging and discharging. The LiMn-oxide spinel showed systematic changes in the electronic structure and also in the microstructure. I will also show how we measured even the Mn L-edge with X-Ray Raman spectroscopy. Then I will show how ceramic proton conductors and metal oxide gas sensors can be investigated with ambient pressure XPS at high temperature and high gas pressure while at the same time impedance spectra are recorded and thus a nice correlation of change of surface electronic structure and electronic transport properties is explained.The dynamics of the proton transport was also studied with quasi-elastic neutron scattering while impedance spectra were taken at high tamperature under hydrated conditions. Even more interesting, we carried out these studies while the proton conducting ceramic was under hydrostatic pressure as high as 1 GPa, and we could show how the compressed lattice slows down the proton dynamics.
Finally I will show how we observe the photoelectrochemical water splitting with soft X-ray NEXAFS valence band spectroscopy in-situ during electrochemical potential control in a liquid UHV-comaptible cell; this was the most exciting experiment because it showed how two different types of electron holes evolve during anodic bias from 200 mV to 900 mV, provided the light was switched on. The two holes go into the charge transfer band and in the upper Hubbard band, repsectively. Their spectral weight changes with different systematic trends and is directly correlated with the water splitting onset potential.
The experiments were done at ALS, SSRL, APS, SINQ, ILL.

We will discuss our recent investigations using INS and quasielastic neutron scattering (QENS) to examine the interaction of hydrogen with pure and metal decorated metal oxide materials, specifically Al2O3, ZnO and MgO. These find widespread use as energy materials especially as oxidation and hydrogenation catalysts. Our studies are geared toward illuminating the microscopic details of the process(es) that underlie the phenomena often referred to as “hydrogen spillover” in order to identify what, if any, role it plays in the catalytic cycle. The term “hydrogen spillover” refers to the diffusion of hydrogen from a surface capable of disassociating H2, onto the surface of an adjoining solid. One of the characteristics of this diffusing hydrogen is that it possesses an electron capable of pairing with an unpaired free radical electron on an adjacent surface noted above, that spillover of hydrogen from a metal to a metal oxide or carbon surface is primarily of interest because most commercial catalysts consist of nanometer sized metal clusters supported on either high surface area metal oxides or carbon, and many catalytic reactions involve hydrogen. More recently, a number of experiments have been performed to determine if hydrogen spillover offers a potentially useful route for improving the storage capacity of various metal decorated high surface area carbon nano materials. It appears that rather than clarifying the microscopic details of the hydrogen spillover concept these experiments added to the confusion concerning the presence and role of the spillover process. Because hydrogen spillover is the fastest of the many spillover processes (e.g. oxygen spillover), and because H2 adsorption is a commonly used method to measure the surface area of supported metal catalysts, it is an important process to understand and clarify. We will present recent INS observations that show that hydroxyl formation on these metal oxide supports takes place only when the metal catalyst is present even at low temperatures. Spectral signatures in both the rotational and vibrational portions of the INS signals underscore this behavior. QENS data establishes that there is substantial translational diffusion at temperatures well below 50K. Similarities and differences of the various support materials will be highlighted. Implications for improving the catalytic performance of these materials will be presented.

All electrochemical processes associated with significant changes in material structure, lattice connectivity or composition, such as electroforming in memristors or initial stages of electrodeposition, typically proceed through the stage of new phase nucleation with subsequent growth of nuclei. The nucleation stage determines the uniformity, direction and nature of the final product. Hence, a first step towards studying and controlling reactions by currents is the elucidation and eventual control of the nucleation mechanism. Despite some recent progress, the factors controlling nucleation kinetics and thermodynamics, including the interplay between local mechanical conditions, microstructure and local ionic profile, remained inaccessible. The tendency of current probing techniques to interfere with the original microstructure prevents a systematic evaluation of the correlation between the microstructure and local electrochemical reactivity. Here, we demonstrate the use of current-based SPM for high resolution mapping of local reactivity and the mechanism of nucleation processes in local electrochemical reactions.
In this work, we have demonstrated two correlated approaches to nucleation processes in electochemical reactions which are associated with surface deformations. The nucleation kinetics have been examined via the study of the bias frequency at which the nucleation process initiates. The current-compliance approach allows the investigation of electrochemical nucleation potential at the scale of 20 nm which provides a pathway for studying the direct correlation between microstructure and electrochemical reactivity on the nanoscale. While the approach has been shown here to work for Li conducting glass, it can be extended to the detailed study of other components in Li-air batteries as well as mapping of ionic motion/concentration in other systems. The technique can be applied to studies of ionic systems including an understanding of nanooxidation, memristive formation and electrocrystallization. The technique also offers the potential for developing routes to understanding mechanisms of nucleation processes in these systems.

Cellulose is the most abundant biopolymer and a major reservoir of fixed carbon on earth. The biocatalysed degradation of cellulose by so called cellulases, a class of enzymes used by many organisms, could effectively produce glucose from plant material which can then be easily transferred to ethanol as a major component for further energy generation or transformation. However, comprehension of the elusive mechanism of its enzymatic degradation represents a fundamental problem at the interface of biology, biotechnology and materials science. The role of synergism between individual enzyme species and its interplay with cellulose regarding disintegration and hydrolysis is still poorly understood. In this contribution, we report on the results of in-situ atomic force microscopy (AFM) investigations which reveals degradation of polymorphic cellulose as a dynamic cycle of alternating exposure and removal of crystalline fibers on the cellulose surface. Direct observation shows that chain-end-cleaving cellobiohydrolases (CBH I, CBH II) and an internally chain-cleaving endoglucanase (EG), the major components of cellulase systems, take on distinct roles: in a first step, EG and CBH II are found to remove primarily amorphous areas of the substrate, thus exposing otherwise embedded crystalline-ordered nanofibrils of the cellulose. In a second step, these fibrils are degraded efficiently by CBH I and supported by CBH II in a cooperative manner, thereby uncovering new amorphous areas. Without prior action of EG and CBH II, CBH I was poorly active on the cellulosic substrate. This leads to the conclusion that synergism among cellulases is morphology-dependent and governed by the cooperativity between enzymes degrading amorphous regions and those targeting primarily crystalline regions. The surface-disrupting activity of cellulases therefore strongly depends on mesoscopic structural features of the substrate: size and packing of crystalline fibers are key determinants of the overall efficiency of cellulose degradation.

Li-ion battery (LIB) anodes that alloy with Li, including Si, Ge, Sn, and Al have specific capacities that significantly exceed that of carbon-based intercalation anodes. However, the large volume expansion and contraction that accompany charging and discharging processes lead to large mechanical stresses that ultimately lead to loss of capacity and failure of the anodes. To better understand the failure mechanism, we cycle a thin film LIB with an Al anode in a scanning electron microscope to measure in real time the nucleation and growth of a highly strained (-44%) Al-Li alloy. We use galvanostatic charging and discharging to control the rate of Li diffusion into the Al anode, and by collecting a series of SEM images in small time intervals we are able to directly correlate the nucleation events of Li-Al with specific peaks in the measured voltage. Based on these observations and ex situ transmission electron microscopy we develop a semi-quantitative description for the mechanism of Al anode degradation that could be extended to other alloy anode materials.

In this work we have explored the mechanical behavior of silicon nanowires while simultaneously alloying the wires with lithium inside a scanning electron microscope. The silicon nanowires have been synthesized using the vapor-liquid-solid technique with Au-colloid particles as catalysts. Mechanical characterization was first performed on pristine silicon nanowires by harvesting them in the scanning electron microscope with a micro-manipulator probe and subsequently fixing one end of the wire at a piezo-actuated nanopositioning system and fixing the other end of the wire to a nominally stationary force sensor. The wires were then subjected to tensile testing while images were recorded for post-processing and stress-strain calculations. Following initial characterization, the wires were slightly strained and the nanomanipulator probe was used to contact the wire with lithium. As alloying between Si and Li proceeds, we are able to track the resulting phase change by analyzing stress relaxation in the wire. The lithiation process was stopped at various time intervals and segments of the wire were preserved for post-mortem analysis. Following this testing, ex-situ transmission electron microscopy was performed to characterize the internal microstructure and chemical composition of the wire. Implications of testing results on the realization of lithium-ion batteries with silicon anodes will be discussed.

Recent advances in instrumentation and electrochemical cell design/platforms have enabled a revolution in in situ characterization for Li-ion battery materials. We describe our recent work developing platforms and methods for in situ study of Li-ion battery materials using transmission electron microscopy (TEM) and scanning transmission x-ray microscopy (STXM). In one approach, an unsealed electrochemical cell, consisting of a nano-scale electrode -- typically a nanowire anode, an ionic liquid or solid-state electrolyte, and a counter electrode, such as lithium cobalt dioxide or lithium metal, is assembled and electrochemically cycled inside a TEM. This approach has been especially powerful for elucidating structural changes -- with atomic scale resolution -- in Li-ion battery anode materials such as silicon, tin oxide, germanium, and aluminum. As a complement to in situ TEM imaging of structure and defects, we have demonstrated chemical state mapping using STXM, a method for providing elemental oxidation state determination with 20 - 30 nm spatial resolution. Lastly, to enable studies of electrode and liquid electrolyte interaction including electrolyte decomposition, we have developed an additional in situ TEM/ in situ STXM platform that uses a sealed thin layer of electrolyte between two electron-transparent silicon nitride membranes. This platform enables analysis of anode or cathode nanoparticles while fully immersed in conventional Li-ion battery electrolytes, such as ethylene carbonate/diethyl carbonate mixtures. The work described here was supported by an LDRD and a NEES EFRC project and was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of Basic Energy Sciences user facility. Sandia National Laboratories is 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.

Developing in-situ imaging and spectroscopic capabilities for the study of materials under tunable environmental conditions achieving high spatial and/or time resolution is a necessary step to quantitatively analyze nanoscale dynamic processes. Corrosion of materials for high temperature applications and catalysis are examples of dynamic phenomena requiring the ability to reproduce localized extreme conditions around the specimen - such as high-temperature, high-pressure, specific oxidizing or reducing atmosphere or a liquid environment. Recent technological advances allow us to image materials with spatial resolutions of ~1 Angstrom or better in aberration corrected (scanning) transmission electron microscopes, (S)TEM, or to investigate processes with temporal resolutions in the microsecond-nanosecond range by using the dynamic TEM (DTEM). These advanced capabilities can be applied to the study of dynamic processes by using environmental stages specifically designed to fit in each instrument. Localized gas/fluid conditions are created around the sample and separated from the high vacuum inside the microscope using hermetically sealed windowed-cells. Here we present our analysis of different experimental and technical aspects determining the attainable spatial resolution and controlling the growth of nanocrystals in the (S)TEM using two environmental holders for experiments in gaseous and in fully hydrated conditions, respectively. These holders are being developed for their use with the second generation DTEM for high time resolution observations of nanomaterials. Therefore, unique qualities of the DTEM that benefit the in-situ experiments with gas/fluid environmental cells will be discussed. The in-situ gas holder has already proved atomic resolution Z-contrast imaging of nanomaterials for pressures up to 800 Torr in oxygen and hydrogen gas[1]. We demonstrate the capability of localized heating for temperatures up to at least 900^oC using an infrared fiber-based laser. With the in situ liquid stage, EEL spectra can be directly recorded and atomic resolution achieved for nanomaterials in a colloidal suspension. It allows continuous flow, controlled growth of nanocrystals and a systematic calibration of the effect of the electron dose on silver nuclei formation in the (S)TEM.[2]
[1] Deshmukh, P.V. et al., In Situ Holder Assembly, U.S. Patent 8178851 (2012)
[2] This work was supported by the National Institutes of Health under NIH grant number RR025032. Pacific Northwest National Laboratory, is operated by Battelle Memorial Institute for the U.S. Department of Energy under Contract No. DE-AC05-76RL01830. Development of in-situ stages was supported by DOE NNSA-SSAA grant number DE-FG52-06NA26213, DOE BES grant number DE-FG02-03ER46057 and NIH grant number RR025032-01.

In situ imaging using (scanning) transmission electron microscopes has proven to be an extremely important and powerful cross-disciplinary scientific technique. In particular nanotechnology and materials sciences have special interest in assembly and disintegration processes, in growth and shape-tuning of (nano)-particles, and, furthermore in mechanistic studies of chemical reactions underlying these processes. However, limitations for in liquid and in situ imaging utilizing electron microscopy arise from experimental conditions required to minimize disturbing electron scatter. Within current sample preparation methods, these limitations are difficult to achieve: nanometre thin and vacuum compatible samples, which are additionally easy to use, reliable and provide relatively high-throughput flow.
Here, we present a nanofluidic sample cell allowing for exquisite control over the liquid layer thickness down to currently 50 nanometre in order to preserve the highest possible spatial resolution for the in situ study of liquid/solutions using electron microscopy. Preparing such ultra thin liquid layers enables us to use a variety of electron microscopes with different lens configurations and electron energies for our imaging experiments. We provide liquid flow through the nanocell by applying differential pressure with feedback control external to the microscope column and therewith allowing for on-the-fly sample exchange within the imaging area.
In this contribution, we show the ability to clearly image gold nanoparticles as small as 5nm, and polymer-based nanoparticles as small as 36nm, over fluid layers as thin as 50nm. Thicker layers, up to 280nm, show clear degradation in spatial resolution but still deliver good quality imaging. We studied the imaging resolution dependent on the liquid layer thickness, obtaining a linear relation between the two.
Furthermore, we demonstrate unidirectional flow in the design concept using gold nanorods pumped directionally through the imaging area upon an applied external force, while tumbling in Brownian motion once the external pressure is released. Having shown the capabilities of our nanofluidic design, we further show preliminary results of in situ imaging, studying gold nanorods to illustrate applications in the study of materials and amyloid fibrils as example of biological applications. Taken together, these systems highlight the variety of applications our nanofluidic cell is able to address. This design is distinguished by straightforward, reliable operation in different, commonly used electron microscopes. In future experiments, we will expand the use of our unique ability to control the path thickness and flow directionality. The latter will be key to enable time resolved electron diffraction in the liquid phase, allowing studies of a wide range of chemical reaction mechanisms on an atomic or molecular level.

In Situ Transmission Electron Microscopy of Electrochemical Reaction in Liquids
Minghua Sun, Hong-Gang Liao, Kaiyang Niu and Haimei Zheng*
Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
*Email: [email protected]
An understanding of the materials transformation in electrochemical processes is critically important for identifying the failure mechanism or improving the power density and lifetime of many battery-related devices. More and more attention has been paid to develop in-situ characterization methodologies to study the dynamics of electrochemical processes. In-situ transmission electron microscopy, which allows for real-time imaging of electrochemical processes in realistic liquid electrolyte environments at high spatial and temporal resolution, has attracted significant attention. Here, we report using an environmental biasing liquid cell operated in a transmission electron microscope to study electrochemical deposition and removal of various metals on the gold electrodes immersed in an aqueous solution. The liquid solution can be maintained in the cell while charge or discharge was performed in the high vacuum microscope. As an example, lead deposition and dissolution in an aqueous solution of lead nitrate with triethylene glycol have been studied in real time. Lead deposition and dissolution on the electrodes was imaged and the current-voltage curve was recorded simultaneously during the charge cycles. Either uniform coating or dendrite structure during deposition was achieved. We further study the influence of surfactants on electrochemical deposition/dissolution and the role of surfactants will be discussed.
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.

Developing controlled and reproducible syntheses is a major goal in many fields of nanoscience, where the nanoscale dimensions and morphology directly determine the properties of such materials. On these length scales, even slight alterations of synthesis conditions and procedures can cause significant changes in final nanostructure and morphology, leading to large variations in properties. This has been shown in the synthesis of mesoporous palladium and Pd alloy nanoparticles within soft organic micelle templates. By employing different synthesis procedures, the resulting porosity, tortuosity, and pore size of the nanoparticles will change, greatly altering their functional properties, such as hydrogen or electrical energy storage characteristics, and the thermal stability of their pore structures. Until recently, such nanostructures have been grown ex-situ and then characterized using various techniques, including electron microscopy. Growth models are then inferred based on those observations, and the synthesis procedure that produced the most favorable properties can be selected. However, these post-mortem characterization techniques cannot provide the information necessary to optimize the synthesis process, in the sense that they follow the evolution of the average structure, but cannot observe the growth over time of an individual particle or specific structure. In order to directly observe the growth processes occurring during synthesis an in-situ nanoscale characterization method is necessary, providing a platform for tailoring the nanostructure synthesis conditions to improve properties.
Using STEM microscopy and an in-situ fluid stage by Hummingbird Scientific, the electron beam induced growth of Pd nanostructures can be recorded with nanometer spatial resolution in real time. We use this in-situ experimental setup to observe the growth of mesoporous Pd within an organic block copolymer templated solution using various drying times and drying environments. In this organic template, the size and morphology of the micelles as well as the structure of the micelle array are dependent on the drying conditions of the solution. Understanding the effects of drying conditions on the resulting micelle template is critical for tailoring synthesis conditions to produce desired Pd nanostructures. This study will develop new insight into the fundamental growth processes of inorganic structures within soft organic templates, and help optimize future synthesis of mesoporous Pd for hydrogen and electrochemical energy storage applications.
Sandia National Laboratories is 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 Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy under contract DE-AC05-76RL01830.

With the increasing demand of energy in recent years, energy storage system such as supercapacitor or lithium battery has been studied intensively. And the study of redox reaction on the interface between electrode and electrolyte becomes an important issue in this field.
In this study, a specimen kit named K-kit was utilized for the in-situ monitor of the redox reaction between solid and liquid interface in transmission electron microscope (TEM). After loading and sealing the reaction materials in K-kit, the reaction solution can be maintained against the high vacuum of TEM with a resolution reaching 10 nm, which makes K-kit a powerful tool for the in-situ monitor of reaction in liquid.
In this work, the observation of a relatively simple redox reaction, the galvanic replacement reaction between silver nanoparticles and gold ions in solution, was conducted to successfully demonstrate the feasibility of in-situ and real-time observation of the redox reaction in K-kit by TEM. The observation revealed that gold would be reduced to form a film, through oxidizing the silver nanoparticles. Therefore, with the successful in-situ observation of galvanic replacement reaction, the study of more complex liquid and solid interface reaction such as that between electrode and electrolyte in a supercapacitor or lithium battery can also be conducted by this approach.

Cobalt nanoparticles are one of the two commercially viable catalyst systems for Fischer Tropsch synthesis. The size-dependent catalytic activity of the cobalt nanocatalyst has been studied extensively. It was found that both surface and mass normalized activities of the small cobalt particles (2-4 nm) are dramatically lower than that of the particles that are larger than 10 nm. This size-dependent effect has been explored by in situ X-ray absorption spectroscopy (XAS); however due to the lack of capacity to directly image the particles in real space, to date the size-dependent reaction pathways of cobalt nanoparticles remain contradictory and elusive. Here, we use the low-dose and low-keV (80 keV) aberration-corrected environmental transmission electron microscopy (ETEM), that are specially poised for the study of soft and light metals, to explore the size-dependent real-time reaction dynamics of cobalt particles ranging from 3-15 nm. Our recorded in situ dynamics directly demonstrate that smaller particles (~4nm) are easier to be reduced as well as more difficult to be oxidized than larger particles. This result suggests that the oxygen adsorption energy is lower for the smaller particles which affect the CO chemisorption and bond opening on the particle surface. This study demonstrates low-dose low-keV real-time structural observation in environmental TEM is key to answering long-standing questions in heterogeneous catalysis.

In-situ studies of catalysts are of high interest since they offer the opportunity to study their atomic and electronic structure in the active state. We present an in-situ environmental transmission electron microscopy (ETEM) study of O₂ evolution catalysis during H₂O splitting based on Pr-doped CaMnO₃ perovskite electro-catalysts. These systems offer the opportunity for fundamental studies of the role of variable Mn valence state, surface structure and defect chemistry for multi step charge transfer. A four electron transfer process at variable potential is required to form molecular O₂ out of two H₂O molecules.
ETEM studies of heterogeneous catalysts are a challenge, since the reactions in the H₂O vapor phase can hardly be observed. We show that the oxidation of silane by free oxygen to solid SiO_2-x can be used to monitor catalytic oxygen evolution. In addition, there is only a very preliminary understanding of the processes stimulated by the high tension electron beam within the sample in a gas atmosphere. Plasmon excitations, electric charging due to secondary electron emission as well as knock on damage has to be studied in details. Therefore, in-situ ETEM studies of catalytic activity in water vapor are combined with in-situ X-ray absorption spectroscopy (XANES) and ex-situ cyclic voltammetry studies. Electron energy loss spectroscopy (EELS) as well as the in-situ XANES reveal that the Mn valence is decreased in the active state. Careful TEM analysis of samples measured by ex-situ cyclic voltammetry and an in-situ bias-controlled ETEM experiments allows us to distinguish between self-formation of the active state during oxygen evolution and corrosion processes at the Pr_1-xCa_xMnO₃-H₂O interface.
Including density functional theory (DFT) calculations, we can correlate trends in O2 evolution activity and defect chemistry in the active state to doping induced changes of the electronic bandstructure in A-site doped manganites.
S. Raabe, D. Mierwaldt, J. Ciston, M. Uijttewaal, H. Stein, J. Hoffmann, Y. Zhu, P. Blöchl, and Ch. Jooss, Adv. Funct. Mater. 2012, DOI: 10.1002/adfm.201103173

Ruthenium Dioxide (RuO₂) is a conversion type negative electrode with a number of attractive properties, such as low resistivity (~30 mu;Omega;#9679;cm) and high theoretical capacitance (1410 mAh/g). Therefore, RuO₂ is ideal for studying conversion type electrodes with applications in Li-ion batteries. The reaction mechanism, however, has only been investigated for large (micron) powders mixed with binders and carbon black, never in its pure form and never with in-situ transmission electron microscopy (TEM). Furthermore very little in-situ work has been done on conversion electrodes in general. In this work, electrochemical lithiation/delithiation cycling of single crystal RuO₂ nanowires was conducted inside a TEM. In the first lithiation cycle, a two-step phase transformation was observed: (1) Li intercalation into crystalline RuO₂ (Tetragonal, S.G.: P4₂/mnm) formed intermediate crystal phase Li_xRuO₂ (Orthorhombic, S.G.: Pnnm), where x is close to 1; (2) further lithiation converted the crystalline LixRuO₂ to nanocrystalline Ru embedded in Li₂O matrix. From the first delithiation process and the subsequent cycles, a reversible conversion reaction between Ru/Li₂O composite and amorphous RuO₂ took place. Part of the reaction was irreversible, a conclusion supported by the HRTEM and HAADF STEM images, showing that some Ru nanoparticles were embedded in the Li₂O after 3 lithiation/delithiation cycles. The nanowires became brittle and cracks were formed during cycling. These results provide a new understanding about the conversion reaction mechanisms in lithium ion batteries, and can be extended to other systems, such as RuO₂ grown or deposited with other systems (ALD, ECD, hellip;), and other conversion type electrodes, such as Fe₂O₃, NiP, FeF₂, etc.
Acknowledgement:
This material is based upon work supported as part of Nanostructures for Electrical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DESC0001160. In addition, this work was performed, in part, at the Sandia-Los Alamos Center for Integrated Nanotechnologies (CINT), a U.S. Department of Energy, Office of Basic Energy Sciences user facility.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy&’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

The widespread integration of nanostructured materials for electrical energy storage will be dependent on developing an understanding of how these materials benefit the long-term performance of a storage device. Desired enhancements in energy density and rate capability need to be balanced with the required material durability, cycle life, and suppression of parasitic reactions that lead to performance degradation. Nanostructured anode materials, such as Si, are of interest because of their ability to accommodate volume expansion upon lithium alloy formation while retaining electronic transport when compared to their meso- to macroscopic structural forms. Significant work has been focused on developing a better understanding of how the process of alloy formation precedes in a Si nanostructure by applying hybrid electrochemical stimulus and characterization methods capable of resolving atomic scale phenomena in real-time. The combination of potential biasing to insert or extract Li ions while conducting Transmission Electron Microscopy is one example of rapidly developing capabilities. Our focus is to integrate quantitative electrochemical control and measurement capability into the “on column” electrochemical TEM experiment so as to conduct galvanostatic charging of individual nanostructures at rates relevant to typical lithium ion battery operation. We are able to correlate the formation of two distinct amorphous Li(x)-Si alloys below the x=3.75 crystalline transition with the rate of injected charge. Chronopotentiometric traces yield unique signatures for these two phases, whose compositional relationship is consistent with selected area diffraction. Additionally, we track the evolution of the structure of the nanowire and the growth of surface films as a function of both cycle number and the rate at which cycling is conducted. Our current studies focus on the use of ionic liquids used as a proof of concept for the study of solid electrolyte interphase formation, its evolution, and impact on charge transport. A new platform that allows full immersion of nanostructures in relevant charge storage device electrolytes will also be discussed. The presented work will explore the use of EC-TEM from a broader perspective of reliability science.
This work was supported by the NEES EFRC and LDRD funding and was performed at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of Basic Energy Sciences user facility. Sandia is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. DOE&’s NNSA under contract DE-AC04-94AL85000.

Silicon-based anode materials are attractive candidates to replace today&’s widely-utilized graphitic electrodes because of their high gravimetric energy density (3572 mAh/g vs. 372 mAh/g for carbon) and relatively low working potential (~ 0.5V vs. Li/Li+). However, the commercial realization still faces challenges due to the structural instability associated with huge volume changes of ~300% during repeated cycling. The volume-induced deformation can simultaneously break away the solid electrolyte interphase (SEI) layer re-exposing the fresh silicon surface to the electrolyte, leading ultimately to irreversible capacity loss and poor cycle life. During real-time studies using our specialized TEM platform, we observe the formation of nano-voids in silicon nanostructures upon delithiation during electrochemical cycling. Such spontaneous nano-voids could provide a built-in buffer to accommodate volume changes during repeated lithiation and delithiation. However, a porous network of voids accessible to liquid electrolytes could also lead to unfavorable SEI growth. These considerations provide opportunities for engineering optimized structures, such as the fabrication of synthetic interfacial layer to behave as an artificial SEI. A detailed understanding of the nano-void formation, along with strategies to mitigate the associated instabilities in nanostructured silicon electrodes will be presented.
This work is supported by the US Department of Energy, Office of Basic Energy Sciences as part of an Energy Frontier Research Center

Solid/electrolyte interface play an important role in energy related materials research. Most of the in-situ investigations concentrate on theanalysis of structural and chemical properties to identify e. g. reaction products, intermediates in complex charge transfer processes, the structure of electrochemical double layers or electrochemically formed films. But in very many cases the material&’s properties are dominated by the electronic structure of electrochemical interfaces in contact formation and electrochemical charge transfer reactions. Applying modern surface science techniques as photoelectron spectroscopy for investigating the electronic structure of solid/electrolyte interfaces to get a better insight into these electrochemical elementary processes is limited by the need of UHV based techniques. We will present during this talk our approach to study the electronic properties of liquid interfaces and wet chemically processed interfaces of solar cells in a quasi-in-situ approach.
Our experimental procedure is mostly based on the application of photoelectron spectroscopy including synchrotron radiation with a specifically designed integrated preparation and analysis system SoLiAS (solid liquid analyser system), which allows to investigate samples after different pretreatments making use of emersion and transfer experiments also with cooled samples as well as in-situ experiment using model surfaces prepared by coadsorption experiments.
As examples of our approach we will present the results obtained with semiconductor/electrolyte interface as used in electrochemical processing steps (etching, cleaning, electrodeposition) and in photoelectrochemical devices. In all cases the surface electronic structure determines the involved charge transfer processes. At first, results obtained for dye injection cells using a combination of emersion and model experiments using adsorption of electrolyte species onto semiconductor surfaces to obtain information on contact potentials and interface electronic density of states will be presented. In addition, examples of wet processing in material science will be presented as e. g. used for the preparation of bulk heterojunction organic solar cells. Finally, results related to the elementary processes in photoelectrochmical cells applied for the water splitting reaction will be discussed.
At we end we will discuss possible improvements of our approach to study the electronic properties of electrochemical interfaces for a wide range of problems, which would be needed for a better understanding of (electrochemical) energy converting devices.

Bilayers of transparent conducting oxides (TCO) and a so-called "buffer layers“ with low conductivity are often employed thin film solar cells or organic LEDs in order to improve multiple interface related issues. These buffer layers may consist of undoped versions of the underlying TCO material or may be formed by a different material, often other wide band gap oxides like Al2O3. TCO/dielectric bilayers are also used as gate structures for transparent thin film transistor devices.
The growth and energy band alignment of Al2O3 thin films on Sn-doped In2O3 (ITO) and F-doped SnO2 (FTO) are compared. The Al2O3 films were deposited by reactive radio-frequency magnetron sputtering or by atomic layer deposition (ALD). Chemical and electronic properties of the films and interfaces are studied in-situ using stepwise deposition and photoelectron spectroscopy (XPS).
During deposition onto ITO, either oxygen implantation (sputtering) or extraction (ALD) occurs, which is identified from changes in the Fermi level position and from the calculation of the growth per cycle. This behaviour is strongly linked to the defect chemistry of ITO, which is dominated by interstitial oxygen atoms. On FTO substrates, the growth behaviour is different and no significantly enhanced growth during the initial ALD cycles can be observed.
The energy band alignments at the various TCO/Al2O3 interfaces can also be derived from the XPS measurements. A significant dependence of energy band alignment on the deposition technique is observed. This can be traced back to a Fermi level pinning in ALD-Al2O3 near midgap, which is associated to the incorporation of H during ALD deposition.

Ultra-thin oxide films are of interest in solid state energy conversion/storage technologies including but not limited to oxide fuel cells, ionic conduction and separation membranes. Understanding their electrochemical properties in-situ may allow one to obtain mechanistic insights of the thermodynamic and kinetic barriers for transport, local electroneutrality and inter-diffusion processes. In this presentation, we will present experimental techniques to investigate high temperature carrier transport in ultra-thin oxides as well as single crystals, especially wherein one can rapidly change the environment locally and observe transient conduction phenomena. Often referred to in literature as electrical conductivity relaxation, performing such experiments in custom micro-probe stations enable us to interrogate oxygen exchange processes in interface-controlled nanoscale oxides, some examples include SrTiO3, ceria. In oxide superlattices, the high temperature electrical conduction measurements allow us to dynamically observe signatures of inter-diffusion and consequently emergence of new phases with distinctly different oxygen pressure dependence on ionic-electronic conduction. In membrane structures, in-situ observations of membrane morphology at high temperatures under chemical potential gradient advances our understanding of the interplay between redox processes that affect lattice expansion/stability and consequently thermo-mechanical integrity that is of great importance in electrochemical energy devices utilizing self-supported films at the few nanometer length scales. Some applications in the context of thin films solid oxide fuel cells will be presented.

The electronic properties of the interfaces between transition metal oxides, and in particular the discovery of a 2D conductivity in heterostructures composed by LaAlO3 and SrTiO3 band insulators, generated new paradigms in condensed matter physics. Recently, 2D electronic states were also found at the bare surface of SrTiO3 (001) crystals, raising several questions concerning the role of the LAO overlayer and about the effective differences between STO/vacuum and LAO/STO interfaces.
Here, by using in situ angle resolved photoemission spectroscopy, we show that these two interfaces share a similar 2D character of the Fermi surface, similar splitting of the in plane and out of plane 3d bands, but significantly different band dispersion and band filling in qualitatively agreement with theoretical predictions. The results show that LAO/STO interfaces are characterised by enhanced two-dimensional localization of carriers and by strong correlations effects not found in the case of the bare STO surfaces.

Wide band gap perovskite structure oxide materials, such as SrTiO₃ (STO), are presently being investigated for use in a wide variety of innovative electronic devices including adaptive electronics and energy harvesting elements [1]. The energy conversion efficiency of nanoscale STO-based thermoelectric energy conversion elements has been reported to be significantly enhanced by quantum size effects, such as the two dimensional electron gas in SrTiO₃/SrTi_0.8Nb_0.2O₃ /SrTiO₃ heterostructures [2]. Nevertheless, a complete understanding of the mechanisms for the reported increase in energy conversion efficiency [3] are missing owing to a lack of understanding of the fundamental properties of oxide-oxide interfaces including knowledge of the band line-ups [4]. To successfully develop STO-based devices for energy applications utilizing quantum size and interface proximity effects, a detailed understanding of the conduction band offsets and the thickness dependence of the transport properties from the mesoscopic to the atomic scale is vital.
In the talk, we will present a study of the in-situ characterization of conduction-band offsets at oxide-oxide interfaces using X-ray photoemission spectroscopy and the thickness dependence of the thermoelectric properties of SrTiO₃/Sr_1-xLa_xTiO₃ and SrZrO₃/Sr_1-xLa_xTiO₃ heterostructures. Characterization of the thermopower, conductivity, and Hall effect will be presented as a function of the Sr_1-xLa_xTiO₃ thickness down to a few unit cells and the observed transport behavior correlated with the conduction band offsets between the oxide films.
[1] J.D. Baniecki et al, Appl. Phys. Lett. 99, 232111 (2011)
[2] H. Ohta et al., Nature Mater., 6, 129 (2007)
[3] Y. Mure et al., Appl. Phys. Lett. 87, 192105 (2007)
[4] R. Schafranek et al, J. Phys. D 45, 055303 (2012)

Platinum is a key component in the performance of electrocatalysts while minimization of the Pt content remains essential to the further development of PEM fuel cell technology. In the case of thin film electrodes conventional vacuum and dc electrochemical deposition techniques yield rough three-dimensional Pt films due to the step-edge barrier to interlayer transport. Recently we have identified and developed a novel self-terminating rapid electrodeposition process for controlled growth of Pt monolayer films from a K2PtCl4-NaCl electrolyte that is tantamount to wet atomic layer deposition (ALD) [1]. Pt deposition is quenched at potentials just negative of proton reduction by an alteration of the double layer structure induced by a saturated surface coverage of underpotential deposited hydrogen, (Hupd). The surface is reactivated for Pt deposition by stepping the potential to more positive values where Hupd is oxidized and fresh sites for adsorption of PtCl42- become available. Periodic pulsing of the potential enables sequential deposition of two dimensional (2-D) Pt layers to fabricate films of desired thickness relevant to a range of advanced technologies. Scanning tunneling microscopy (STM), surface enhanced infrared spectroscopy (SEIRAS), electrochemical quartz crystal microbalance (EQCM) and X-ray photoelectron spectroscopy (XPS) were used to characterize Pt films produced by the pulsed deposition scheme. In situ STM experiments reveal three levels of height contrast that are ascribed to the deposition of two layers of Pt on top of Au(111) surface. The first Pt layer coverage is ~85% whereas the second layer is ~10%. In this talk, the details of self terminating 2D Pt deposition will be discussed using in-situ STM images, electroanalytical measurements and spectroscopy techniques.
1. Y. Liu, D. Gokcen, U. Bertocci, T.P. Moffat, “Self-terminating growth of Pt by electrochemical deposition” in press.

In this contribution we are going to present the results of the experimental investigation of oxygen kinetics in layered cobaltites of general formula REBa2Co5+x (RE=rare earth; 0L. Malavasi, C. Tealdi, C. Ritter “In-situ time-resolved neutron diffraction investigation during oxygen exchange in layered cobaltites" Angew. Chem. Int. Ed. (2009) 48, 8539-8542

Li-ion batteries have seen widespread application as secondary batteries in numerous applications in consumer electronics, and have attracted recent attention for various forms of electric vehicles. One particularly attractive material for the cathode is the Ni-rich system of LiNi_0.8Co_0.15Al_0.05O₂. These materials are being explored as a replacement to LiCoO₂, as they offer several performance improvements, including higher energy density and lower cost. However, these materials have demonstrated a significant increase in impedance and capacity fade during ageing, or upon cycling at elevated temperatures. Additionally, when in highly delithiated states, the reduction of Ni ions during thermal cycling releases oxygen from the crystal structure, which can lead to both thermal runaway and violent reactions with the flammable electrolyte.
We have utilized a variety of in-situ characterization methods to understand the mechanisms associated with the thermal degradation of LiNi_0.8Co_0.15Al_0.05O₂ materials, as a function of their delithiation / charge state. By combining time-resolved synchrotron x-ray diffraction and mass spectrometry, we directly show that these materials undergo a specific sequence of phase transformations - from layered to disordered spinel to rock salt - as a function of temperature, and directly correlate these phase transformations with the evolution of oxygen from the microstructure. In-situ observations in an environmental transmission electron microscope confirm these global average measurements on the nanoscale, and allow us to kinetically track the evolution of oxygen from the surfaces of the nanoparticles into their bulk. In-situ spectroscopic results - from XAS and EELS - allow correlation between electronic structure changes and the resulting phase transformations. Finally by performing these same thermal treatments in-situ to the TEM and in the presence of excess oxygen, we show that it is possible to suppress these phase transformations to significantly higher temperatures, thereby suggesting that methods to protect the surfaces from oxygen evolution could lead to significant enhancements in the safety performance of these materials. Throughout the presentation, the insights gained from complementary in-situ techniques will be highlighted.

Oxygen evolution and reduction through heterogeneous catalysis have attracted much attention because they play important roles in renewable and sustainable energy applications. Traditional battery technology is based on intercalation mechanism and no catalytic process is involved. Recent breaking-through in rechargeable lithium oxygen batteries introduces OER and ORR into battery system for the first time. After intensive screening active catalysts in the past few years, α-MnO2 have been identified as the most active electrocatalyst for both reactions, while the fundamentals of how this catalyst is involved in OER/ORR during electrochemical charging/discharging haven&’t yet been explored.
Our previous studies in photocatalytic oxygen evolution from water suggest that Mn3+ exhibits much higher activity in oxygen evolution than Mn4+ and it is known that Mn4+ is only active for oxygen reduction reaction from the literature. Our hypothesis is that α-MnO2 in the composite oxygen cathode switching its oxidation state during charging and discharging due to lithium intercalation/de-intercalation. At initial discharging, Mn is +4 in α-MnO2 and it acts as ORR electrocatalyst. At the end of discharging, the oxidation state of Mn is close to +3 because lithium intercalation into α-MnO2 significantly reduces the oxidation state of Mn. When the battery is on charging mode, Mn3+ in Lix-α-MnO2 acts as oxygen evolution site to decomposition of lithium peroxide to lithium and oxygen. During deep charging to 4.5V, the lithium ions intercalated into α-MnO2 structure are removed and Mn atoms are back to Mn4+ again. Such switching mechanism greatly promotes the electrocatalytic activity of α-MnO2 nanowires in both ORR and OER during cycling at the same system.
Because the catalyst in the electrochemical cell is in a complicated environment (gas, liquid and solid, three phases), in-situ techniques are appreciated. In this presentation, we will discuss our recent progress in using in-situ X-ray absorption techniques to monitor the oxidation state of Mn during the electrocatalytic processes at real time and to elucidate the electrocatlytic mechanism of ORR/OER on the surface of α-MnO2. We have successfully fabricated a custom electrochemical cell, which allows us to monitor the electrocatalyst structure evolution in real time when subjected to high flux synchrotron X-ray source. This represents the first attempt to utilize in-situ XAS techniques to study the mechanism of OER and ORR in an electrochemical cell at real time. The XAS data clearly show the oxidation state of Mn shifted to 3+ during discharging and returned to 4+ when the cell was charged. This in-situ technique will help us reveal the detailed mechanism in electrocatalytic OER/ORR and advance our understanding of the fundamentals.

The Schottky barrier heights at the interface between metallic electrode materials (RuO2 or Pt) and BaTiO3 single crystals or Pb(Zr,Ti)O3 ceramic sample are studied using X-ray photoelectron spectroscopy with in-situ control of ferroelectric polarization. The procedure provides quantitative values for the Fermi level position at the interface in dependence on polarization state. The experimental procedure and results for different ferroelectric / electrode systems are presented.

We present a new quantitative imaging method, based on accumulated single molecule trajectories, to map and probe surface charge heterogeneity. Using a fluorescent cation as a probe molecule, we found that surface charge has a dramatic affect on the local adsorption rate, primarily through its influence on near-surface ion concentrations. Other physical measures, including residence time and diffusion coefficient, provided complementary information about the probe-surface interaction that can be obtained only through a single molecule approach. We present spatial maps of surface charge based on each of these dynamic probe properties.

Resistive switching and metal-insulator transitions phenomena observed in condensed-matter systems are of interest from the perspective of both fundamental physics and applications. Governed by several different mechanisms, they not only expand our understanding of the correlation effects, ionics, interaction between charge, spin and orbital degrees of freedom, but also find use in memristive electronics, non-volatile memories, smart glasses, Mott transistors etc. Calcium-doped bismuth ferrite (CaBFO) is one of the prospective materials for these applications as at doping level of ~ 10% it exhibits a bias-driven two orders of magnitude insulator-metal transition. The reversible electronic conductivity change is thought to be linked to dynamics of the oxygen vacancies introduced by Ca-doping, and thus this material presents an interesting case of electrochemically-controlled resistive switching. Here we report on the polarization and relaxation phenomena in CaBFO epitaxial film and their relationship to the resistivity switching studied through the transport measurements between lateral electrodes, as well as by Band-Excitation and Single Frequency Kelvin-Probe Force Microscopy (BE- and SF- KPFM) and Scanning Impedance Microscopy (SIM). Whereas the transport measurements give macroscopic information on the ion diffusivity and film conductivity, the SPM techniques show local real-time nanoscale responses and polarization dynamics, yielding relaxation amplitude and times maps of the interelectrode region. Varying the temperature we additionally acquired thermodynamic information on the activation barriers of the studied phenomena. Comparison and modeling of the obtained data following the Hebb-Wagner approach allowed us to establishing a direct link between the oxygen vacancy motion and gradual insulator-metal transition. The mechanism of transition is discussed in details and the contributions of different scenarios to it are given.
Research was supported (E.S., S.J., S.V.K., I.K.) by the U.S. Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division. A portion of this research was conducted at the Center for Nanophase Materials Sciences (E.S., S.J., S.V.K., I.K.), which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.

Because of their enormous interface area to volume ratio, nanoparticle (NP) systems are intrinsically in a non-thermodynamic equilibrium state and tend to evolve via coarsening processes driven by the reduction of the total interface free energy. Fundamental knowledge on the coarsening mechanisms and their rates is highly desired because the phenomenon can be considered as a thermodynamic tool in order to tailor the NP system properties by changing their size and number density. In this contribution we report on the thermal stability and microstructure evolution of Pb nanoparticle systems submitted to high temperature (400 to 1100 °C) thermal treatments and in-situ TEM electron irradiation. The samples were prepared by implanting Pb ions into 200 nm thick thermally grown silica films kept at room temperature, following a procedure described elsewhere in previous ex-situ investigations [1]. In comparison with these ex-situ results, in-situ experiments reveal that the combination of high temperature and electron irradiation from the 200 kV beam used in the TEM observations significantly affect the microstructure evolution of the system. We demonstrate that, at temperatures above 400 °C, the electron beam enhances NP nucleation and atomic Pb redistribution. In addition, at 1100 °C, the electron irradiation induces the migration of liquid Pb NPs embedded in the film, which can reach distances much higher than the particle diameter, thus promoting a migration and coalescence coarsening process. The in-situ TEM thermal treatments and electron irradiation were registered using a high frame-rate CCD camera. A careful video analysis indicates that the NP migration process presents a Brownian-like behavior. The determination of effective diffusion coefficients from individual particles as a function of their radius suggests that the NP migration process is governed by an electron-irradiation-enhanced interface diffusion of matrix atoms, discussed considering either elastic atomic displacements or adiabatic breakdown of atomic bounds of matrix atoms at the particle interface region. The present experiments introduce a model case system that tackles the stability of nanoparticles, enlightening the effects of energetic particle irradiation-annealing treatments and identifying issues that could hamper their long-term applications in radiation-harsh environments as in space or nuclear sectors.
[1] F. P. Luce, F. Kremer, S. Reboh, Z. E. Fabrim, D. F. Sanchez, F. C. Zawislak and P. F. P. Fichtner, J. Appl. Phys. 109, 014320 (2011)

The synthesis and study of soft-donor uranyl complexes can provide new insights into the coordination chemistry of non-aqueous {UO2}2+ leading to a better understanding of reactivity, bonding and structure within uranyl complexes outside of traditional oxygen-donor systems. Recently, the tunable N-donor ligand 2,6-Bis(2-benzimidazyl)pyridine (BBP) was employed to produce novel uranyl complexes in which the {UO2}2+ cation is ligated by anionic and covalent groups with discrete chemical differences. In this work we investigate the electronic structure of the three uranyl-BBP complexes [(UO2)(H2BBP)Cl2], [(UO2)(HBBP)(NC5H5)Cl], and [(UO2)(BBP)(NC5H5)2] via near-edge X-ray absorption fine structure (NEXAFS) experiments, density functional theory-based ground state total energy calculations, and NEXAFS simulations using the excited electron and core-hole (XCH) approach [1]. Evolution of the structural as well as electronic properties across the three complexes as a result of changing the coordination around the uranium site is studied systematically. A self-consistent DFT+U scheme [2] is considered in order to take into account strong electron correlation effects due to the presence of localized f-electrons. Total energy calculations provide insight into the observed variations in structural properties across the three complexes, showing that the non-planarity in the equatorial co-ordination plane of Uranium is driven by steric effects. Computed N K-edge and O K-edge NEXAFS spectra are compared with experiment and spectral features assigned to specific electronic transitions in these complexes. The role played by residual solvent molecules within crystalline samples in modulating the spectra is also investigated. Furthermore, studying the variations in the energies of specific spectral features arising from N K-edge absorption provides a clear picture of ligand-uranyl charge transfer in these systems.
Acknowledgements:
This work was supported by the Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory under U.S. Department of Energy Contract No. DE-AC02-05CH11231
//
References:
[1] D. Prendergast and G. Galli, X-ray absorption spectra of water from first-principles calculations, Phys. Rev. Lett. 96, 215502 (2006).
[2] M. Cococcioni et al., Linear response approach to the calculation of the effective interaction parameters in the LDA+U method, Phys. Rev. B 71, 035105 (2005).

The storage and the retrieval of hydrogen are active research areas in the pursuit of hydrogen as an energy carrier. Metal hydrides are good candidates for reversible solid-state hydrogen storage, and MgH$_2$ has good gravimetric and volumetric hydrogen-storage capacity. However, the kinetics of the dehydrogenation reaction is slow, and the temperature of hydrogen desorption (above 350 degrees C) is higher than desired. Variations in synthesis, processing etc. are being attempted to alter the thermodynamic and the kinetic properties. It has been found experimentally that addition of transition metals (TM), often in small quantities, improves the kinetics and brings down desorption temperature. Such observations prompted us to explore how TM additives could modify properties of bulk MgH$_2$. Experimentally it is very difficult to distinguish between the various factors that influence the dehydrogenation reaction. First-principles calculations allow us to isolate the roles played by TM impurities in MgH$_2$. An understanding of the mechanisms is crucial to improve the process and to identify more efficient additives.

The (de)hydrogenation reaction proceeds through diffusion processes, mediated by native point defects such as vacancies and interstitials. Reducing the formation energy of relevant defects increases their concentrations, resulting in higher diffusion rates and an enhancement in kinetics. Using first-principles calculations with a screened hybrid functional (HSE) we study the formation energies of native point defects in MgH$_2$. Charge neutrality imposes equal concentrations of positive and negative charged defects and determines the position of the Fermi level in the band gap. The presence of TM impurities (Ti, Fe, Co and Ni) causes the Fermi level to shift according to the position of the transition-metal acceptor/donor levels in the band gap. This shift can bring down the formation energy of native defects. According to our calculations, we find all of the TM additives, in either interstitial or substitutional configurations, may cause such a shift in the Fermi level, and hence increase the concentration of the hydrogen vacancies that govern hydrogen diffusion. Our proposed mechanism, backed by first-principles calculations, provides an explanation for the enhanced rate of dehydrogenation observed experimentally upon addition of TM impurities to MgH$_2$.

Separators play an important role in the operation and safety of lithium ion batteries (LIB). These films are responsible for facilitating ionic transport as well maintaining electronic isolation between the anode and cathode. A separator must therefore possess adequate mechanical strength and chemical stability to ensure proper operation for the lifetime of the LIB. A detailed understanding of the mechanisms which give rise to a separators mechanical properties and response is important for cell design as well as accurate modeling of a battery&’s response to applied stress. The most common type of separator found in commercial cells is nano-porous polyolefin sheets. These are made through a highly controlled process of extrusion, heating/cooling, and stretching which results in an anisotropic film with ordered nano-pore structures that penetrate the entire thickness of the film. Some permutations of this design use layers of different polymers (generally polypropylene and polyethylene) in order to create a safety shut-down mechanism that closes the pores when a cell exceeds a certain temperature to prevent thermal runaway. An array of separators including those of the single and triple ply varieties were examined using both ex situ and in situ X-ray diffraction techniques. Changes to the crystalline structure and texture of each material were assessed as a function of strain. A comparison between dry and electrolyte wetted samples were also performed in an attempt to better understand the true behavior of these materials in an actual cell. The tensile strain behavior of these materials was correlated with observed structural changes, and the results and implications of this work will be discussed.

Recent research has focused on the Li-rich solid-solution layered cathode materials Li2MnO3-LiMO2 (M=Co, Ni etc), which exhibit a discharge capacity of more than 200mAhg-1 when operated above 4.6V. However, the mechanism of the charge-discharge reaction, which is the origin of the discharge capacity, has not been clarified. In order to reveal the change in valence state of transition metals (TM), TM K-edge XANES was measured, but it appears to be somewhat complicated to discuss the reaction mechanism from only the experimental results. [1] In this study, we performed first-principles calculations of TM K-edge XANES spectra for Li-rich layered cathode materials using our computational code [2] based on the projector augmented-wave (PAW) method to investigate the atomic and electronic structure of TM.
We calculated Mn K-edge spectra for MnO, MnO2, Li2MnO3, and spinel LiMn2O4, and confirmed that experimental spectral features can be reproduced well. [3] Furthermore, we calculated Ni and Co K-edge spectra for substitutions in [Li1/3Mn2/3] layers of Li2MnO3, and found that the valence states and the substitution sites are different between Ni and Co.
[1] A. Ito et al., J. Power Sources, 196, 4785 (2011). [2] T.Tamura et al., Phys. Rev. B 85, 205210 (2012). [3] T. Tamura et al., Modelling Simul. Mater. Sci. Eng. 20, 045006 (2012).

Silicon carbide is an important material with application in both state of the art circuitry and in extreme environment applications such as high radiation fields. There are hundreds of polytypes of silicon carbide; of these, the 3C polytype structure holds promise in next generation nuclear reactor material selection. Due to its excellent high temperature mechanical properties and previously investigated radiation tolerance, 3C silicon carbide is being considered for new fuel designs, including generation IV reactor TRISO fuel particles. In these fuel applications, the silicon carbide layer contains the fission particles emitted by the nuclear fuel. Radiation testing and material design down to the microstructure scale is vital to demonstrate SiC application and expand the range of operation of this material with respect to power density, fast neutron fluence, and temperature. In this study, the electrical properties of silicon carbide are utilized to study the accumulation of radiation damage. Novel electronic devices with thin films of 3C-SiC deposited via CVD on silicon substrates are fabricated for ex-situ and in-situ measurement of radiation effects on electrical response in an effort to elucidate the onset of and mitigation pathways for radiation damage. These devices include electrically isolated silicon carbide films for resistance/resistivity measurements, pn junction IV measurements, and MOS capacitor CV measurements. It is expected that the electrical properties will shift as a result of damage creation in the SiC lattice, potentially at fluences less than those where measurable defects are observable in analysis of the microstructure. Using these fabricated devices, we monitor changes in electrical properties as samples are being irradiated. A Keithley 4200 Semiconductor Characterization System is used to make electrical measurements as silicon carbide samples are being irradiated. From this analysis it may be possible to detect the onset of radiation damage in the silicon carbide lattice before defects become visible using microstructural imaging such as TEM. This study will provide a greater understanding of radiation damage accumulation in silicon carbide as well as new methods for detecting the onset of radiation damage in materials

SrCu2O2 (SCO) thin films were obtained by annealing strontium-copper oxide films grown on silicon substrate by Metalorganic Chemical Vapor Deposition (MOCVD). The transformation pathway of the films during annealing was studied by the combination of in-situ Raman and X-ray diffraction (XRD) experiments, as well as ex-situ Fourier Transformed Infrared Spectroscopy and XRD measurements . This transformation is characterised by the decomposition of SrCO3 and CuO into a Sr14Cu24O41 phase when the films are annealed in oxygen, and by the transformation of this phase into the expected SCO phase after subsequent annealing under Ar. In-situ studies revealed that the SCO phase is preserved at room temperature only when the film is cooled down very quickly.

Stimuli-responsive polymer layers consisting of surface-tethered macromolecules have been widely applied in many technological areas, including fabrication of sensors, regulating cell cultures, and in controlling wetting and adhesion properties of surfaces. Owing to their fascinating conformational changes in response to variation of a number of environmental parameters, this class of materials has also attracted the scientific community focussed on renewable and sustainable energy applications. For example, the anti-fouling properties of polymer brush layers has been investigated, while recently poly(N-isopropylacrylamide) has been suggested as technologically appealing rooftop coating to control water adhesion by varying its temperature, and therewith enable management of heat transfer out of buildings.
Poly(N-isopropylacrylamide) (PNIPAM) is one of the most frequently studied stimulus-responsive polymers. The thermally induced collapse transition of PNIPAM in aqueous liquids as well as in mixed solvents has been investigated extensively. At temperatures below the lower critical solution temperature (LCST), the polymer is soluble in water due to cooperative hydration, which is caused by a positive correlation between adjacent bound water molecules. Due to steric interactions, consecutive sequences of bound water appear along the PNIPAM molecule. Upon heating the system to temperatures above the LCST, which is around 32°C in aqueous media, each sequence is considered to collectively dehydrate, resulting in a collapse of the grafted molecules. PNIPAM chains show strong hydration behavior below the LCST, while above the LCST they adopt a dehydrated and compact form. By utilizing the hydration/dehydration effect, PNIPAM layers are expected to have applications in, e.g., permeation-controlled filters, tissue engineering, and actuators.
Here we demonstrate the potential of in situ spectroscopic ellipsometry for the investigation of the chain segment density profile and layer thickness during the temperature-induced, reversible collapse-expansion transition of PNIPAM grafted layers. We studied PNIPAM films with variable grafting densities in aqueous systems, which were produced by atom-transfer radical polymerization. In our attempt to obtain a realistic quantitative description of the thickness of our swollen PNIPAM layers, various models were implemented to fit the ellipsometric data. As expected, we found that the swelling ratio is strongly dependent on the grafting density. From the ellipsometry results, the density and thickness variation accompanying the collapse transition across the lower critical solution temperature (LCST) was characterized. The collapse can be adequately explained by considering the PNIPAM film to consist of two layers: (i) a dense layer near the surface and (ii) a more diluted layer on the side of the film exposed to the solvent. Analysis of the optical response reveals a gradient density profile within these layers.

Energy storage devices, such as batteries and supercapacitors, are critical for a global clean, renewable energy future. For the development of the next generation of energy storage devices, novel materials are crucially needed to increase storage capacity (e.g., longer range for electric vehicles). Silicon and sulfur are promising anodes and cathodes in Li-ion batteries, respectively, because they have high specific charge capacities compared to current electrodes. However, both these materials have issues limiting performance. We have used in-situ transmission X-ray microscopy (TXM) and X-ray diffraction (XRD) to investigate structural and morphological changes in Si and Ge anodes and sulfur cathodes during operation.
Sulfur has a high theoretical specific capacity, but suffers from the loss of active material and parasitic reactions due to the solubility of polysulfides in the electrolyte. For Li-S batteries comprised of micron-sized sulfur/carbon particles, XRD showed that the reformation of crystalline S at full charge is dependent on the sulfur/carbon morphology and crystalline Li2S (reported in ex situ XRD studies) does not form in situ. TXM tracked morphological changes in the sulfur particles. We found that the sulfur/carbon composite particles did not found to dissolve significantly during the discharge, suggesting that the soluble polysulfides are (at least partly) trapped in the carbon matrix. Our results suggest that more complete encapsulation of the sulfur will result in a Liminus;S battery with a longer lifetime [1].
Silicon nanowires (SiNWs) have been recently developed to overcome failure from the large volume expansion during Li-ion insertion. From in situ XRD, we found that metastable Li15Si4 phase formed at deep lithiation voltages. However, by modifying the SiNW growth temperature formation of this phase was prevented and cycling performance improved. Recently we have demonstrated 3D in situ TXM of nanostructured Ge anodes (see figure). From this we will be able to quantify the volume change in a single particle and directly observe the development of cracks during operation.
[1] J. Nelson, S. Misra, Y. Yang, A. Jackson, Y. Liu, H. Wang, H. Dai, J.C. Andrews, Y. Cui, M.F. Toney, J. Am. Chem. Soc. 134, 6337minus;6343 (2012).

In situ or also called in operando techniques are indispensable for the characterization of energy storage systems like lithium ion batteries. Limiting processes or fatigue mechanisms, which occur during the cycling of the battery, can be revealed in detail, which furthers the continuous development of new materials for cathode and anode side.
In situ powder diffraction studies using synchrotron radiation sources enable a high time resolved and detailed investigation of structural phenomena. Namely the evolution of lattice parameters, microstructure formation, phase transformations and even changes in the atomic positions can be determined quantitatively.
We will present a new in situ setup at P02.1 - a 60 keV beamline at the storage ring PETRA III in Hamburg, Germany. An overview is given about crucial parameters like signal to noise ratio, contributions to the background and measurement time per diffraction pattern. The latter can be reduced to the region of seconds - at least 30 times faster in comparison to previously used setups.
The final instrumental resolution mainly depends on the beam direction and the geometrical parameters, which are set for the 2D detector. We measured the instrumental resolution in dependence of the named parameters and related the results to the detection limit of microstructural effects, which can possibly arise during the electrochemical cycling.
The outstanding performance of P02.1 is exemplified by in situ powder diffraction results of a high voltage cathode material with low symmetric monoclinic structure. The limitations of the electrochemical performance are related to structural phenomena like anisotropic lattice parameter changes or distortions of the atomic structure. Those structural analyses are accompanied by ex situ investigations like XPS or SEM. For instance crack propagation was observed in the crystalline material after charging which illustrate underlying fatigue mechanisms, quantitatively disclosed with the presented in situ technique.
The Bundesministerium für Bildung und Forschung is gratefully acknowledged for financially supporting this work within the HE-Lion consortium and grant no. 05K10ODA.

Organic electronics have been considered a leading candidate to make transparent and flexible electronics at a low cost. The main building block of an organic thin film transistor (OTFT) or organic photovoltaics (OPVs) are organic semiconductors (OSCs), which acts as the charge transporting layer. It is preferred that organic electronics are formed using solution processing methods, so that the time frame for processing is more compatible with industrial fabrication time scales. We have previously shown that the solution shearing method (SSM) is a process that improves OTFT performance for a range of OSCs, and the method is compatible with roll to roll industrial processing. This method can also tune the molecular packing in OSCs, enabling high performance OTFTs and OPVs by tuning the electronic properties without changing the OSC chemical structure. In SSM, it is difficult to study the morphological and polymorph growth that enable high OTFT performance. Not only does the thin film crystallize at a fast time scale, the evaporation front, where the crystal grows from the solution, is very small. The entire evaporation front can be less than 200 microns. Thus, the solution evolves into a crystallized thin film within seconds, and within an area less than 0.2 mm wide.
We use an X-ray ‘microbeam&’ at the Cornell High Energy Synchrotron Source, with a beam width of < 20 microns, in conjunction with a high speed CCD detector to resolve and follow crystallization from solution of the OSC during solution shearing. We have collected up to 100 frames per second X-ray images, and are able to create grazing incidence x-ray diffraction movies to easily see how crystallization occurs in the solution shearing system in real time. We also use an optical microscope trained at the evaporation front, which we can use to collect optical videos of the evaporation front at up to 10,000 frames per second. Being able to simultaneously study kinetic crystallization using both optical and X-ray movies helps us understand how different processing conditions result in various crystal morphologies and polymorphs. We study the model OSC 6,13-bis(triisopropyl)-silylethynyl pentacene (TIPS-pentacene) and the polymer poly 3(hexyl-thiophene) (p3HT) in various organic solvents in order to see how SSM based crystallization occurs. We are able to study drying times of the thin films, the evolution of the solvent evaporation front as well as polymorph formation of different OSCs in real time.

Mesoporous anatase (TiO2) beads have been used to prepare electrodes for high performance dye-sensitized solar cells, producing greater than 10% solar to electric power conversion efficiency. These high efficiencies results from the high surface area of the materials, the connectivity of interparticulate mesopores and the enhanced light scattering from the size of the beads (diameter ~800 nm). Efficient solvothermal synthesis routes for mesoporous anatase may be developed by better understanding the reaction mechanism and kinetics. To this end, an in situ and time resolved synchrotron X-ray diffraction study of this process has been conducted at the Australian Synchrotron. The solvothermal syntheses were conducted in quartz glass capillary microreactors while diffraction patterns were collected every 1-2 min. This allowed the induction period and the rate of crystallization from amorphous precursor to anatase to be determined for various synthesis conditions. This presentation describes the effects of time, temperature, precursor size and type (with or without HDA), and solution composition on the reaction kinetics, as well as on the crystallite size and morphology. The synthesis mechanism will be discussed based on combined results of in situ XRD and post microscopic examination.

The layered Ruddlesden-Popper phases of A_n+1B_nO_3n+1, such as La₂NiO₄ and Sr₂TiO₄, have attracted much attention as potential materials for solid-oxide fuel cell cathodes, oxygen separation membranes, and thermoelectrics. The structure of Ruddlesden-Popper phases consists of n consecutive perovskite layers, ABO₃, alternating with AO rock salt layers along the crystallographic c-axis. However, the multivalent nature of the transition metals, intergrowth defects, and variable oxygen stoichiometry make the stabilization of these layered phases challenging, especially in epitaxial thin film form. In order to understand the fundamentals of layered oxide film growth, we employ in-situ surface x-ray diffraction (SXRD) during layer-by-layer growth of c-axis oriented Sr₂TiO₄ and La₂NiO₄ on SrTiO₃ (001) substrates by oxide molecular beam epitaxy at the Advanced Photon Source. For the case of Sr₂TiO₄, our results show that the synthesis of the double SrO layer followed by TiO₂ dynamically reconstructs back into the SrTiO₃ phase, which demonstrates that during thin film deposition other pathways under growth conditions can give rise to new structural arrangements. These data are supported by computational results that show that the layer stacking energetics favor the experimentally observed restructuring. In contrast with Sr₂TiO₄, the growth of La₂NiO₄ involves the stacking of polar LaO⁺ and NiO₂^- layers. This raises the question of how polarity mismatch at the interface with the SrTiO₃ substrate will influence the growth process as well as how Nature dynamically handles compensation of the polar surface. A detail comparison of these two cases will be presented, demonstrating the power of quantitative x-ray probes for understanding the process of thin film synthesis.

One of the key subjects in materials research for clean energy are sorption processes for storage of gases such as H₂ and CO₂. The changing crystal structure during the sorption processes and details of reaction mechanisms can be studied in situ by X-ray diffraction (XRD) in dedicated sample environments.
In situ high-pressure XRD studies mainly belonged to the domain of synchrotron facilities and dedicated instruments. Recent developments have extended the application area of high-pressure studies to the home laboratory systems: (i) the availability of a commercial chamber for X-ray diffractometers which allows pressures of different gases as high as 100 bar and temperature as high as 900 °C; (ii) the availability of hard radiation on a laboratory system (Ag and Mo radiation) and (iii) multidimensional X-ray detectors. In this contribution we present high-pressure studies on H₂ and CO₂ storage materials on a standard laboratory X-ray diffraction system.
We have selected two cases: CO₂ sequestration in p-tert-butylcalyx[4]arene and H₂ storage in ammonia borane. P-tert-butylcalyx[4]arene is a non-porous material which belongs to a family of cyclic polyphenolic compounds that have been extensively studied as host materials. It undergoes a structural transition to a phase which absorbs 7 wt% of CO₂ at mild conditions¹. Ammonia borane (NH₃BH₃) is well known to be able to store high amounts of H₂ (~12 wt%) and to release it fast at moderate temperatures (below 150 °C)².
The phase transitions recorded during the in situ measurements are instrumental in the understanding of the desorption and/or sorption properties as well as reaction mechanisms. Furthermore, fast detection of X-ray diffraction patterns allows the determination of intermediate phases, onsets of reactions and reversibility of sorption processes.
References:
¹P.K. Thallapally et al., Nature Materials, Vol.7, 146 (2008);
²Z. Xiong et al., Nature Materials, Vol.7, 138 (2008).

Core-shell electrocatalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) have been attracting increasing attention over recent years as a means of improving both catalyst activity and the utilization of Pt within the material compared to Pt-only nanoparticles. To fully understand the origin of the activity benefits and how the structure of these electrocatalysts is altered in the electrochemical environment, full in situ characterization is required. Extended X-ray absorption fine structure spectroscopy (EXAFS), wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) are techniques which, especially when combined in situ, have the potential to provide the level of structural information required. EXAFS data can be analyzed to give the local coordination environment of the element being investigated in terms of the number of, identity of and distance to neighbouring atoms; WAXS data is used to determine the structure of the crystalline regions of the sample; SAXS can provide details of the size and/or shape distribution of the nanoparticles. To investigate the sensitivity of these techniques to materials of this nature, a series of well-defined Pd-core, Pt-shell carbon-supported catalyst nanoparticles has been prepared with the Pt-shell thickness varying from 0.5 to 4 monolayers. EXAFS, WAXS and SAXS measurements have then been conducted in situ using synchrotron radiation to investigate the effect of shell thickness on the structural response to an applied electrode potential, both for the freshly prepared samples and for those exposed to electrochemical ageing via potential cycling. EXAFS was found to be sensitive to the variation in shell thickness and to the changes in structure resulting from the applied electrode potential. WAXS was again sensitive to the differences in the structure of the samples as a function of the shell thickness and applied electrode potential, with complementary information being obtained to that from the EXAFS. Neither the EXAFS nor the WAXS data showed significant differences in the structure of the samples following electrochemical ageing. The SAXS data obtained showed that the technique was not sensitive to the effects of applied potential on these materials under the conditions used, however, significant differences were seen in the samples following electrochemical ageing. The advantages and limitations of each of these characterization methods when applied to these materials will be discussed, along with the benefits of a combined approach.

Ionomer membranes are one of the central components of electrochemical devices such as fuel-cells and solar-fuel generators. This devices rely in the interaction of ion-conducting polymers, such as Nafion, and inorganic electrocatalytic components to transport charges, reactants and intermeadiates to reaction sites. This work takes advantages of novel X-ray characterization tools, with sub-second time resolution, to elucidate the effects of interfacial interactions in structural dynamics of ionomers upon water absorption. Using in situ grazing-incidence X-ray scattering (GISAXS), we demonstrate that interfacial interactions can significantly affect the internal morphology and dynamics of Nafion films during water uptake. Thin-films cast on substrates passivated with hydrophobic self-assembled monolayers result in preferential parallel orientation of conducting domains, while films prepared on polar SiO₂ surfaces result in isotropic orientation of these domains. GISAXS patterns also demonstrate that upon thermal annealing of Nafion thin-films, static crystalline domains form near the substrate interface which further restricts the swelling of the material. These morphological characteristics directly affect the macroscopic water uptake behavior of films, where the matrix crystallinity and parallel orientation of ionomer domains limits the maximum water absorption of films from humidified environments. The results presented in this work provide a better understanding of the behavior of Nafion at interfaces and can help explain the absorption dynamics of bulk membranes.

In recent years, the ubiquitous deployment of Li-ion batteries for mainstream consumer applications has lead to increased demands on the battery performance. With the increasing adoption of hybrid- and fully-electric vehicles, both manufacturer and consumer scrutiny of cell performance continues to rise, to increase the cost-effectiveness of the vehicles. Satisfying these demands is becoming increasingly difficult, as traditional investigation techniques provide only a limited understanding of the operational parameters.
Recent research has pointed toward microstructure as being a critical indicator of final battery cell performance. Advancements in the field of high-resolution in-situ TEM and XRD are providing valuable insight into the functioning of the electrode particles, along with in-situ X-ray diffraction measurements for functional studies of the crystallographic parameters. This high-resolution work is providing new insights into the fundamental principles of battery cell operation, particularly on the specially-designed cells that have been manufactured for these studies.
In the context of commercial battery research, electrode microstructure is becoming the key indicator for understanding electrochemical performance. In the work of Kehrwald et. al. (J. Electrochem. Soc., 2011), X-ray micro-CT imaging was used to show that the localized nature of ionic transport through the inter-particle network is highly inhomogeneous; this is hypothesized to have a measureable effect on the final cell performance, and represents a departure from traditional battery electrode microstructure modeling assumptions.
Here, we present a progress update on expanding the role of non-destructive lab-based X-ray microscopy (XRM) within Li-ion battery research. In the context of this work, a commercial Li-ion coin cell battery was imaged intact in both its charged and discharged state, exploiting the non-destructive nature of X-rays for time-dependent (“4D”) studies of microstructure evolution. The resulting particle and pore networks were then correlated to each other using the technique of digital volume correlation (DVC), in order to track the migration of the electrode particles on a particle-to-particle level. Analysis of this result revealed a positionally-dependent particle dilation, which is believed to be due to variable levels of lithiation/de-lithiation. Using this high-resolution x-ray microscopy technique, studies such as these may be carried out in the future in-situ or in-operando, without any specialized sample preparation.

Realization of lithium ion batteries with high C-rate capabilities and energy density will require the development of roadmaps for achieving favorable porous electrode microstructure through the selection of active materials, additives, and electrode processing conditions. To develop such roadmaps, a clear understanding of battery microstructure is needed. We report the use of synchrotron radiation x-ray tomographic microscopy (SRXTM) to obtain statistically significant volume (700x700x100 mu;m³) 3D reconstructions of porous electrode microstructure of transition metal oxide active materials.
We present a technique for preparing porous electrodes for SRXTM and a segmentation algorithm that allows identification of individual particles. We validate the algorithm by showing that the reconstructed particle size distribution (PSD) is in agreement with the experimentally determined PSD obtained with laser diffraction.
We use data from Li(Ni_1/3 Mn_1/3Co_1/3)O₂ (NMC)-based cathodes, prepared with varying weight percent of carbon black and binder (2-5%) and under different compressions (0- 2 kbar), to show how this technique can be applied to visualize the microstructure, to calculate parameters such as electrode porosity and tortuosity, and provide greater insight into the observed electrochemical performance. In addition to insight into electrode morphology, we demonstrate that the technique is capable of resolving features on the sub-particle level such as particle fracture, which is observed here under high compression conditions.

As solution-processing of organic solar cells emerges as a viable manufacturing process, supported by recent reports of organic photovoltaic (OPV) devices with efficiency close to 10% prepared using laboratory-based methods, such as spin-casting, there is increasing urgency to complement traditional trial-and-error methods with rigorous in situ investigations to keep achieving rapid improvement of performance. Here, we report on time-resolved investigations of the formation and nanoscale phase separation of the polymer:fullerene bulk heterojunction (BHJ) layer during spin-coating using grazing incidence small and wide angle X-ray scattering, spectroscopic reflectometry and ellipsometry, and fast videomicroscopy. The combination of these techniques in the case of P3HT semicrystalline donor polymer and PCBM fullerene acceptor allows us to probe and quantify the initial behavior of the solution ejection and thinning, film formation in terms of molecular crystallization and phase separation. OPV device fabrication and testing are also complemented by plan-view and cross-sectional energy filtered transmission electron microscopy (EF-TEM).

The coupling between electrochemical and mechanical behavior is of great importance for battery electrodes, particularly in light of the large volume changes associated with intercalation. Here, we introduce a method for in-situ analysis of micro-mechanical properties during electrochemical cycling of electrode materials. An electrochemical cell is integrated into a Nanoindenter (MTS G200) which allows the real time measurement of the electrode contraction/expansion during dis-/charge and the determination of the mechanical properties like elastic modulus, yield stress and toughness at different states of charge. The setup is suitable for studying bulk crystals, single particles or granular electrodes during electrochemical cycling in an ionic liquid electrolyte.
Preliminary studies during Li intercalation into FePO4 and Si show stable and reproducible results for both the electrochemical and mechanical behavior. Both materials show a clear change in hardness and modulus as well as volume changes, measured using the indenter in constant small load mode. For example, tests on Si show that an irreversible decrease in modulus and hardness occurs during lithiation, which could clearly be attributed to amorphization. Similarly, a granular composite electrode containing FePO4 oxide particles of approx. 100nm diameter showed clear changes in the mechanical properties presumably due to an increase in the size of the particles due to lithiation. Next tests will probe the extent of reversibility in the mechanical behavior of Si and single FePO4 particles. These initial tests set the stage not only for correlating mechanical behavior with the extent of lithiation but also for investigating the effect of stress and deformation on the electrochemical potential.

Increasing attention has been recently paid to materials which form alloys with lithium metal such as Si, Sn, Sb, and Ag, to be used as lithium-ion battery (LIB) electrodes. Although these alloying materials provide a larger specific capacity than graphite, they generally suffer from poor cycling behavior due to a large volume change during lithium cycling. To improve battery life it is important to understand how these materials change mechanically in each battery cycle and degrade over time inside a battery. In this work, we report utilization of an innovative MEMS sensing platform for diagnosing in situ electrochemical reaction-induced mechanical changes in LIB electrodes.
The miniaturized MEMS sensing platform consists of a membrane-based sensor system integrated with a LIB electrode. A silicon nitride membrane is created at the bottom of a 12 mu;m cavity in a silicon wafer, and an anodically bonded Pyrex wafer forms an optical Fabry-Perot cavity above the membrane. A deep (480 µm) battery cavity is etched on the other side of the membrane, and it is coated with LIB electrode material. The “battery side” of the device, when combined with electrolyte and a metallic lithium counter electrode, forms a lithium half cell. The Fabry-Perot optical interferometry principle is used to evaluate membrane deflection caused by dynamic changes in the mechanical properties of the electrodes. In order to enable both electrochemical testing and optical detection of Fabry-Perot fringe patterns, the MEMS sensing platform is incorporated into a custom, hermetically sealed package based on a standard coin cell with a transparent window. Thin-film silicon electrodes were used to evaluate platform performance, due to the large volume expansion Si undergoes during battery operation.
The Fabry-Perot fringe pattern observed in the circular membrane cavity consists of dark and bright concentric circles. Diameter, intensity and number of fringes change during battery cycling. Analysis of multiple thin-film Si electrodes with different thickness has reproducibly shown that upon lithium intercalation the Si film initially deforms elastically, resulting in rapid change of Fabry-Perot fringe radius. This is followed by Si being deformed plastically under compressive stress, which corresponds to the constant Fabry-Perot fringe radius. Upon lithium extraction, the electrode first undergoes elastic straining in the opposite direction leading to a tensile stress; subsequently it deforms plastically during the rest of the charge. These results are in good agreement with previously reported data for thin-film silicon electrodes.
In summary, this novel in situ experimental methodology enables investigations of electrochemically driven stress generation and deformation that lead to degradation and failure of LIB electrodes. The platform provides the unique ability to observe electrochemically-correlated mechanical changes in a wide variety of thin-film electrode materials.

We report the application of magnetography as a novel method to determine the state of charge (SoC), state of health (SoH) and localization of defects in commercial Li-ion batteries (LIBs). The method is non-invasive and non-destructive and can be applied during operation. It is based on the spatially resolved measurement of the induced magnetic field B generated by current flow inside the LIB during cycling. A measurement standard setup had been developed: applied current rate, scan distance, scan surface and time were optimized for a prototype measurement system. The developed measurement procedure offers high reproducibility (~0.1%) and the possibility of the characterization of the different spatial components of the field: Bx, By, Bz. The results are supported by parallel IR-imaging. The percentage deviation (PD) between B-images for different SoCs (determined from open circuit voltage UOCV) for a given current load revealed significant differences. A deviation for B of up to 20% between SoCs of 90% and 10% was found. The comparison between a reference and thermally treated (aged) LIBs at different SoCs reveals a similar trend for both samples with a reduced deviation for the aged sample. The SoC-dependent variation of B is attributed to the change of the magnetic properties of the cathode material upon cycling. This is due to a change of the magnetic susceptibility (chi;) upon varying the amount of intercalated lithium in the transition metal based (LixNi1/3Mn1/3Co1/3O2) intercalation cathode. In addition it is possible to localize induced mechanical defects by analyzing the derivation of the in plane-component of the magnetic field. The method turns out to be a sophisticated characterization tool to be applied particularly for large LIBs for energy storage and vehicles applications.

Microporous coordination polymers (MCPs) represent a rapidly growing class of sorbents whose surface areas have exceeded those achievable with traditional porous materials such as activated carbons, zeolites, or porous oxides. Owing to their potential utility in adsorption-based fuel storage technologies, new MCPs are continually being reported, but despite promising crystallographic structures, the experimentally obtained porosity of these materials often falls far below expectation. Positron annihilation lifetime spectroscopy (PALS), an antimatter-based technique that can provide both averaged and localized pore structure information in situ, is particularly well-suited to the study of MCPs. This technique operates on the principle that positronium, the bound state of an electron and a positron, will have an annihilation lifetime directly related to the pore size and shape in which it annihilates. In this presentation, PALS is shown as a viable platform for the determination of the causes and mechanisms for underperformance in MCPs. Materials defects such as surface collapse and interpenetration will be discussed. Furthermore, degradation of these materials during exposure to thermal and chemical stresses can be tracked by PALS. Finally, PALS is shown to provide an in situ view of pore structure during gas adsorption, and provides insight on new routes to optimizing the pore space in these materials to maximize both gravimetric and volumetric gas storage.

Engineering efficient artificial photosystems for catalytic and photovoltaic (PV) purposes is a major challenge for the development of viable solar fuel generators. One possible route toward this goal is to employ molecular catalysts covalently attached to semiconductor light absorbers through molecular linkages. The effect of such linkage on local electronic structure, however, remains an important question. Scanning tunneling microscopy (STM) is a useful tool for answering this question since it enables characterization of molecular interfaces at the atomic level. Here we describe our progress at measuring the structural and electronic properties of single organic molecules adsorbed to a p-doped GaP(110) surface. Low temperature STM was used to explore the surface chemistry and reactivity of GaP(110) by exposing UHV-cleaved GaP surfaces to sub-monolayer coverages of ethylene (C2H4) and iodobenzene (IC6H6), the latter being a candidate linker for connecting catalysts and PV molecules to semiconducting light absorbers. We have characterized the local electronic structure at these molecular interfaces via scanning tunneling spectroscopy and DFT calculations. Our high-resolution STM images in combination with DFT calculations provide a detailed picture of the molecular adsorption geometries, probing the strength and stability of the C-Ga bond. The insights gained here provide guidance for future attachment strategies involving improved molecule/semiconductor interfaces.

From the very start of their discovery, X-rays have been known for their penetrating power. This allows their application in a wide range of environments. Typically, X-rays in the energy range from 10-20 keV are used, but the present generation of synchrotron radiation sources can also provide intense X-ray beams with energies of 70 keV and higher, with a significant increase in scope of the environments used. Here the use of X-ray diffraction for the in situ study of crystal growth will be discussed. By proper selection of the observed diffraction spots, the signal from the atomic-scale growth interface can be observed, despite the large penetration depth.
Three examples will be discussed: the medium-pressure growth of GaN crystals from a Ga solution, the growth of oxide materials using pulsed-laser deposition and semiconductor growth from the liquid phase. When growing from a liquid, it is found that the liquid in contact with the growing crystal surface shows partial ordering that influences the resulting crystal structure.

Soft-x-ray absorption spectroscopy (XAS) is a technique that can reveal a wealth of information about a heterogeneous catalyst because it can be used to characterize the adsorbed reactants and products as well as the chemical state of the metal catalyst surface. Traditionally, for surface science, the technique has been restricted to ex situ or high vacuum studies because soft x-rays interact strongly with gases.
To overcome this limitation, a novel gas cell has been developed to study heterogeneous catalysts in situ, using synchrotron-based XAS at the Advanced Light Source in Berkeley, CA. The gas cell can operate at up to 5 bar and at temperatures up to 400 C, so that catalysts can be characterized in realistic reaction conditions. The gas cell employs a Si3N4 window to isolate the high pressure reaction cavity from the high vacuum of the synchrotron beamline. Absorption spectra are collected by measuring total electron yield current, which is surface sensitive. An IR laser is used for heating rather than a resistive heater, a new feature which prevents electrical noise from interfering with the weak total electron yield current.
The gas cell was used to follow the oxygen K-edge and cobalt L-edge during the catalytic hydrogenation of carbon monoxide (Fischer-Tropsch synthesis) on cobalt nanoparticles of varying diameters (4, 10 and 15 nm). Fischer-Tropsch synthesis is an important reaction for energy production because it provides a way to derive liquid hydrocarbon fuels from carbon sources besides crude oil, such as coal or biomass. By in situ XAS, we discovered that the first step of the reaction, the dissociation of carbon monoxide, is suppressed on smaller particles and enhanced on larger particles. This can explain what has been observed the literature; particles under 5-10 nm are less active for producing hydrocarbons.

In-situ x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES), combined with electrochemistry, are powerful tools to investigate the chemical nature and local structure of electrocatalysts under active conditions. In the present work, we performed in-situ XAS and XES measurements on a bifunctional manganese oxide (MnOx) catalyst with high electrochemical activity for oxygen-evolution reaction (OER) and oxygen-reduction reaction, at varying electrochemical potentials under alkaline conditions. X-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) reveal that exposure to a potential of 0.7 V, corresponding to ORR, leads to a disordered Mn3O4 phase with negligible contributions from other phases. After increasing the potential to a highly anodic value of 1.8 V, relevant to the OER, we observe an oxidation of the disordered Mn3O4 phase to a phase similar to birnessite MnOx and a minor phase, likely corresponding to Mn3O4. XES results support the XAS conclusions that oxidation state of Mn under ORR conditions is close to 2.7 and that under OER conditions is slightly less than 3.7. We have also used rapid-scan XANES and energy dispersive X-ray Kβ1,3 emission spectroscopy to study the nature and kinetics of the phase transition between the OER and ORR catalysts.

In-situ studies of electrochemically driven lithiation and delithiation of materials for lithium ion batteries promise an improved understanding of the underlying intercalation mechanisms. We report on initial studies using a miniature lithium ion battery based on a STM-TEM holder inside a transmission electron microscope. The cathode consists of Li metal with a native oxide layer which acts as a solid electrolyte. Single crystalline silicon TEM lamellae or nanowires are used as anodes. An electric potential between anode and cathode drives the lithiation process. The Si nanowires show behavior consistent with what has been reported in the literature, in that they show a clear increase in volume during lithiation. In contrast we observe the formation of isolated line or planar defects inside the Si lamellae anodes without significant volume changes. This effect is preliminarily attributed to the different geometry of the Si lamellae relative to the nanowires. We attempt to interpret the presence of the defects in terms of possible models for very early stages of lithiation.

Triboemission comprises the emission of low energy electrons and photons, the eventual formation of micro-triboplasmas, and the possible charge-initiated tribochemical reactions on the surfaces under contact. Electron triboemission is often seen as a case of electron exoemission, but such low-energy output may be just a fraction of the total electronic excitation on the surface, the majority of which may proceed as internal currents. The dynamics of these related surface phenomena have been investigated by different techniques, which are discussed in this work; in particular, the authors have obtained extensive data indicating that electrons and photons are produced from mechanical surface work, particularly from surface oxides and semiconductors under contact sliding in vacuum. They are designing an instrument to detect charged emissions in controlled atmospheres and gas flows to further investigate possible mechanisms of low-energy plasma formation, which may include emission from micro-fracture phenomena. This paper also discusses the existing body of work on triboemission, and the possible use of the developed measurement techniques as novel probes for surface processes.

It has become increasingly important to develop energy storage devices with large energy density, fast charging capability and durability, and Li-ion battery has been one of the most widely studied energy storage devices. However, a lot of technical challenges remain to be overcome and much of the physical phenomena are not clearly understood yet.
Until recently, most characterization methods have been bulk-scale and provided only area-averaged quantities. However, the information only from area-averaged quantity limits our fundamental understanding on the electrochemical kinetics and its evolution significantly. There are numerous unknowns about what happens at atomic scale. For example, we are not clear about the actual influence of defects, doped species and topographical variations on the solid electrolyte interface (SEI) formation, Li ion intercalation/de-intercalation processes and ionic diffusion along the electrode. There have been efforts of nanoscale characterization, but they were mostly based on ex-situ experiments. Due to the restrictions that common characterization tools impose (such as the necessity of high vacuum condition, material pre-treatment, etc.), in-situ observation of electrode evolution has been highly restricted.
We present an AFM-based in-situ nanoscale electrical characterization on a Li-ion battery. We employed atomic force microscopy as the main tool to perform nanoscale electrical characterization of Li-ion batteries. We customized AFM probes and modified electrical measurement schemes for the study. In order to uncover localized variation of intercalation/de-intercalation, SEI formation and associated ionic diffusion processes, electrical and strain signals was simultaneously processed under various set of combined dc and ac stimuli. Additionally, through the localized observations, we could observe the influence of defects/edges of graphene layers, metal oxide particle and the interfaces between these on the electrochemical activity, diffusion and other morphological/electrical changes.

In this study, we have attempted to characterize the photovoltaic effect in real-time measurement of photoinduced current in an organic photovoltaics(OPV) using photoconductive atomic force microscopy (PC-AFM). To irradiate a light with specific wavelength, the Xenon lamp and monochromator have been adopted with PC-AFM system. And the range of wavelength was controlled from 200nm to 1100nm. The Organic solar cells, prepared via electro-chemical processes including spin coating of solutions which were mixed with P3HT, PCBM and a 9.09 wt % with 1,2-dichlorobenzene (DCB) as a solvent, were investigated in this study in terms of their electrical and optical properties including open-circuit voltage (Voc), short-circuit current (Isc), fill factor, external quantum efficiency (EQE) and efficiency, employing a few recognized test methods. In the PC-AFM analysis, we used a metal-coated conducting cantilever tip as the top electrode of the solar cell and light from a Xenon lamp was irradiated on the PC-AFM scanning region. As the light wavelength varies from 200nm to 1100nm, the current value also changes in the range from 5 nA to 20 nA at 80mu;W/cm2 light intensity, because different amount of electrons and hole carriers are generated by the photovoltaic effect. The ratio of the conducting area at different conditions was calculated, and it showed a behavior similar to that generated by a photoinduced current. On analyzing the PC-AFM measurement results, we have verified the correlation between the light wavelength and photoinduced current of the organic solar cell in nanometer scale. We compared the experiment results from an identical specimen via KFM and PC-AFM, respectively verifying that the scanning probe technique is very effective both in photovoltaic effect measurement and mechanism establishment.

The interface between thin films of organic semiconductors and transparent conducting electrodes is important for charge injection and extraction in many optoelectronic devices. Energy band alignment at these interfaces is not always predictable and can be strongly dependent on substrate preparation and growth conditions. There is therefore value in the direct monitoring of interface formation with techniques that provide parallel information. ZnO is a transparent semiconductor that is attractive as an electrode material and also as a UV absorbing optoelectronic material. We have monitored the surface energetics of ZnO single crystals using real-time electron spectroscopy during in-situ processing for both Zn and O terminated surfaces and have studied the adsorption of vacuum-deposited organic films of fullerenes and phthalocyanines on these surfaces in comparison with ITO-coated glass substrates. The growth of the organic overlayer is similar on all substrates with the phthalocyanine producing the more uniform films. There is however significant charge transfer that modifies the band-bending on both sides of the interface. Real-time characterisation provides the time and thickness dependence of the morphology and interface energetics for each interface without interrupting the growth.

With a projected two-fold increase in worldwide energy consumption during the next 50 years, there is an urgent need for new energy sources to meet the growing demand. A particular emphasis on low- or zero-emission sources (e.g. solar) necessitates the development of more efficient materials for EES with improved capacity and charge/discharge stability. Although numerous materials exhibit great promise for incorporation into next generation devices, their properties are often not well understood and many offer high initial specific capacities only to suffer rapid and unacceptable losses with repeated charge-discharge cycling. In situ characterization of the evolution in electronic structure of these electrode materials during repeated charge-discharge cycling is fundamentally important for more fully understanding the processes of charge storage and degradation, which, in turn, is essential for the development of new EES materials with tailored properties and improved performance. X-ray spectroscopies provide ideal tools with which to obtain enhanced insight into the origins of electrode behavior in EES systems due to their capabilities for direct, element specific, characterization of the electronic densities of states. To date, in situ studies of EES materials have primarily focused on hard x-ray experiments due to the challenges associated with UHV compatibility and high photon attenuation of cells for soft x-ray measurements. Nonetheless, the use of soft x-ray spectroscopies to EES systems is vital since they provide complementary information that cannot be obtained via hard x-ray studies. We report the development of a capability for in situ soft x-ray emission spectroscopy and x-ray absorption spectroscopy studies of EES materials and will discuss experiments focused upon the x-ray spectroscopy characterization of a series of nanoporous carbon electrodes for capacitive energy storage. Prepared by LLNL under Contract DE-AC52-07NA27344.

The development of environmental transmission electron microscopy (TEM) has enabled in situ experiments in a gaseous environment with high resolution imaging and spectroscopy for many systems. However, many of the more relevant catalytic systems are operated at much higher pressures than the ~20 mbar achievable in the current state of the art environmental TEM. Gas flow stages, in which the gaseous environment is contained between two thin membrane windows (typically SiN), have been demonstrated at reported pressures of up to several atmospheres. While the potential to work at realistic pressures is attractive, the design of many gas flow stages does not allow accurate knowledge of the pressure at the location of the sample, which depends on parameters such as the spacing between the windows, that varies significantly from one experiment to the next, or even with changes in flow rate for a given setup. A reliable means of estimating the pressure near the sample, for each experiment, is needed. To that end, electron energy loss spectroscopy (EELS) is used to assess the electron inelastic mean free path through a gas flow stage at different input gas flow rates, in situ, within the TEM. The inelastic mean free path of an electron within a given gas is directly related to the density of that gas. As the thickness of the gas volume can be independently, accurately measured by TEM imaging of the top and bottom windows, it is possible to achieve an estimate of the gas pressure via the ideal gas law. Inelastic scattering is fairly abundant at higher gas pressures, so these measurements can be made quickly and locally prior to or during an experiment, and with a relatively small electron dose. This approach will be demonstrated for nitrogen gas, and is applicable for the other gasses that have typically been used for in situ TEM studies, as it depends only upon measuring the total inelastic:elastic scattering ratio and not a particular core-loss edge.

The search for low cost, renewable, environmentally friendly energy solutions has led to an extensive amount of research being done on various energy materials and energy storage devices. Studying the microscopic structure of these energy materials, and their morphological and chemical changes in operando, gives us great insight on how these materials work. Here, the advantages of using full-field transmission x-ray microscopy (TXM) with a synchrotron radiation source for 2D and 3D imaging are presented. The single image field of view is ~30 mu;m, which can be extended up to millimeters if multiple images are stitched together. This allows for shorter imaging times of larger areas within materials in comparison to scanning-based systems. By utilizing Fresnel zone plates, the resolution of the TXM system at SSRL can be as low as 30 nm, allowing for high-resolution imaging of small features in these materials. Because the depth of focus is on the order of tens of microns, utilizing this technology simplifies sample preparation and allows for in situ and operando imaging of devices. With the wide tunability of the bright synchrotron radiation lightsource, we are able to perform chemical speciation through various x-ray absorption spectroscopy (XAS) techniques, including 2-energy tomography and x-ray absorption near-edge structure. Investigations of battery electrode particles and catalyst particles using these techniques will be presented.

We have developed a method to study the detailed surface structure of single crystal oxide thin films in a controlled ambient pressure environment with synchrotron x-ray diffraction, capable of addressing challenges in areas such as catalysis, chemical sequestration, ion conduction, and sensing. A custom-built micro-reactor and new modular chamber mounting system was integrated into a diffractometer for surface x-ray scattering experiments at Sector 12ID-D at the Advanced Photon Source. The integrated micro-reactor (<50ml), consists of a small x-ray transparent Be dome, and a sample heater mount that is capable of reaching temperatures exceeding 600°C in a pure oxygen environment. The gas stream composition exiting the micro-reactor, important for the study of many energy systems, can be measured with an in-line gas quadrapole mass spectrometer (QMS) for real-time data collection or a gas chromatagraph (equipped with QMS or TCD). Using this micro-reactor system, we combine advanced x-ray scattering methods and ambient pressure in-operando studies to investigate catalytic processes. Model single crystal epitaxial oxide thin films were grown by pulsed laser deposition on single crystal substrates including ferroelectric BaTiO₃, and mixed conductors of La_1-xSr_xMnO₃ and SrCoO_3-δ. The structure determination of these functional thin films will be discussed in terms of the relevant x-ray techniques including surface x-ray diffraction, grazing incidence x-ray diffraction, and resonant x-ray scattering with Coherent Bragg Rod Analysis (COBRA). Additionally, the results from preliminary in-operando catalysis measurements will be presented along with strategies for applying this method to low surface area model oxide catalysts and low turn-over-frequency model oxide films. We believe that this method benefits the development of oxide thin films and other materials towards current energy initiatives.

Alloying has been a successful approach to improve the reactivity of transition metal heterogeneous nanoparticle (NP) catalysts. For example, the addition of particular “dopant” atoms to the NP surface and interior has been observed to increase turnover, improve selectivity, enhance resistance to deactivation, and promote multifunctionality; these observations have been attributed to changes in surface atom arrangements and electronic structure. However, the reactivity of alloyed NP catalysts often evolves during reaction, particularly at higher operating temperatures, where atoms can easily diffuse and alter surface composition and structure. Dynamic rearrangements, coupled with adsorption of strongly bound intermediates, can make “stable” surface compositions which promote high reactivity difficult to achieve over a large range of operating conditions. As such, obtaining insight into improving the activity and selectivity of NP alloy catalysts is a challenging task.
In this work, Ag-doped Pt nanoparticles (NP) were tested for continuous-flow C2H2 hydrogenation reactivity and CO adsorptionminus;desorption from 100 to 300 °C to investigate how submonolayer levels of an insoluble metal dopant can distribute on steps and terraces of a NP surface and modify reactivity [1,2]. Ag incorporation onto Pt step and terrace sites, and resultant temperature-dependent desorption behavior, were probed using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) with CO. At low coverage, Ag appeared to occupy Pt step sites; for higher coverage, Ag occupied both step and terrace sites, which was observed to lower the CO desorption temperature. The catalytic influence of sub-monolayer Ag incorporation into Pt NP surfaces was also probed in-situ during batch and continuous-flow C2H2 hydrogenation. NP catalysts were found to be highly active and selective for C2H2 to C2H4 hydrogenation. Ag-doped Pt NP catalysts with ~0.5 ML Ag showed increased selectivity with temperature up to 200 °C, in contrast to commercial hydrogenation catalysts (e.g., Pt, Pd, PdAg) that are known to have activity-selectivity tradeoffs. Highly correlated reactivity and DRIFTS data highlight the importance of step site blocking and desorption from Pt during selective C2H2 hydrogenation. Furthermore, measurements over multiple reaction cycles from 100 to 300 to 100 °C demonstrate how immiscible metal dopants can preferentially modify NP surface compositions and promote active, selective, and stable catalysts over large temperature operating windows.
[1] L.C. Jones, Z. Buras, M.J. Gordon, J. Phys. Chem. C 116, 12982 (2012).
[2] L.C. Jones, M.J. Gordon, J. Phys. Chem. C, DOI: dx.doi.org/10.1021/jp308107g.

As reactions of Li-ion batteries and fuel cells are generally occur in aqueous solution, in-situ analysis of such reactions in aqueous is essential for improving the properties of these energy generators. Though FT-IR measurement is a powerful method to investigate the reactions in organic solvents, it is seldom applied for aqueous solution as water exhibits large absorption in mid-IR range. In literature, there are several reports which describe FT-IR spectrum of water using a reflectance configuration and an attenuated total reflection (ATR), though the signal-to-noise (S/N) ratio is not enough to observe the reactions. Thus, it is required to develop a FT-IR measurement method to observe the reactions in aqueous at a high S/N ratio.
In this research, we developed a novel cell for measuring FT-IR spectrum of aqueous solution under transmission configuration and the super critical state of water is in-situ observed. The body and windows of the cell were made of HASTELLOY C-276 alloy and CVD diamond respectively, since they are corrosion-resistant and mechanically strong materials up to the supercritical state. The temperature (263 - 683 K), pressure (vacuum - 30 MPa) and flow rate of the water were controlled. Optical path length is adjusted to be about 1 micron meter by using a metal spacer.
Temperature and pressure dependence of transmission IR absorbance of ultrapure water was observed up to super critical state. Changes in the fundamental vibrational modes of stretching, bending and rotation of water molecules were observed. These absorption peaks were broadened because of the hydrogen bonding, which is outstanding characteristic of the water compared to other normal liquids. According to the neutron scattering experiment by Postorino et al. [Nature 366 (1993) 688], hydrogen bonds were disappeared in the supercritical state. Our in-situ FT-IR results, however, indicate that hydrogen bonds remain in the super critical state, i.e., broadened absorption peaks are still observed in the supercritical state, and peak position of the stretching vibration showed continuous blue shift with increasing temperature. In addition, we also detected an absorption component which might be corresponding to local tetrahedral configuration of H2O molecules in the supercritical water.
As a result, the cell developed enables us to measure the in-situ transmission FT-IR spectra of water at high temperature and high pressure quantitatively. Therefore, various application fields including energy material research would be expected.

Sum Frequency Generation (SFG) vibrational spectroscopy has emerged as a valuable tool to study intermediates on the surface of metal catalysts. More recently, research in heterogeneous catalysis has moved away from perfect single crystals (e.g., Pt(111) and Pt(100)) to colloidal nanoparticles with well-defined size and shape. We use SFG and kinetic experiments to assess alkene hydrogenation reactions on platinum nanoparticles. Changes in product selectivity are correlated to changes in reactive intermediates observed with SFG. We have characterized the mechanism of the butadiene hydrogenation reaction and the adsorption of cyclohexene.

Interaction of hydrogen with graphene and graphene hydroxide has been studied using a combination of adsorption measurements and neutron vibrational spectroscopy. Hydrogen adsorption measurements demonstrated that graphene displays significant hydrogen storage capacity. Hydrogen uptake capacity for graphene was found to be significantly larger than graphite oxide and graphite. Neutron vibrational spectroscopy yielded useful information including the occurrence of the rotational mode of molecular hydrogen on graphene at 119 cm-1, slightly below the free rotor, which is in agreement with the value observed for H2 rotation on graphite. Effect of attaching hydroxyl groups onto the graphene surface and incorporating lithium into graphene has also been explored and will be discussed.

Purified syngas from coal or biomass gasifiers can be utilized through subsequent catalyzed processes for the production of fuels and chemicals, as well as for fuel cell-based power generation. Capture of CO2 during syngas preparation provides benefits, both in reducing greenhouse gas emissions as well as through facilitating the generation of optimal syngas (H2/CO) compositions through driving the water gas shift reaction equilibrium. CO2 capture must occur at the same (warm) temperature as water gas shift in order to preserve energy efficiency.
MgO based double salts are promising absorbents for CO2 absorption in the temperature range of 300-400 °C. We have previously described their performance under both temperature and pressure swing absorption/desorption cycles. Notably, NaNO3, a byproduct of the originally reported synthesis, has been found to play a significant role in facilitating this absorption. For example, the CO2 uptake via formation of a Na2Mg(CO3)2 double salt increased by a factor of two, from ~8 wt.% to ~16 wt.% in the presence of NaNO3. We have also found that the presence of NaNO3 leads to enhanced absorption of CO2 by pure MgO as well. A high initial capacity of ~70 wt.% has been observed with a mixture of MgO and 15 wt.% NaNO3. In situ XRD studies of the phase transformations occurring during absorption and desorption cycles will be described. The NaNO3 must be present in the molten form in order to enhance the CO2 absorption by MgO and MgO-based double salt absorbents. Understanding the interactions of molten NaNO3 with these solid absorbents and with CO2 at the interface is essential to predicting performance. We will describe studies using a variety of in situ techniques, including IR, NMR, TEM, and SEM aimed at increasing our understanding of this complex and interesting system. Theoretical analysis using density function theory calculations will also be described that support experimental results.

Fuel cells, redox flow and lithium ion batteries have received increasing attention during the last years due to their promising potential in environmentally-friendly energy conversion and storage. However, despite numerous efforts, their nationwide application has not yet come into sight. This is in part due to the materials applied in those devices, which are not yet up for competition.
In order to develop materials with superior properties, their reaction mechanisms and degradation phenomena need to be understood in detail. This can be done using sophisticated spectroscopy and imaging techniques in combination, in situ, time and space resolved etc. One example where a deeper insight is required is the carbon component in electrochemical energy applications: carbon is used as electron conducting additive in lithium ion batteries (LiB), as support material in fuel cells (FC) and as porous electrode in redox flow batteries (RFB). Carbon, however, is not easy to study, since it is a low Z element and mostly amorphous in these applications. Thus, it is not accessible by X-ray diffraction (XRD), for which long range order in the material is needed. Also in-situ X-ray techniques do not appear to be applicable, since a minimum X-ray energy for material&’s penetration in the keV range is needed, while the carbon&’s absorption edge is at 280 eV.
In this work, it will be shown how X-ray Raman spectroscopy and total XRD/PDF can be used to understand reactivity and degradation of carbon in RFB and FC. Apart from the material&’s chemistry, in energy applications very often also the structure of the porous electrode is of importance. The focused ion beam technique (FIB/SEM) has been applied to image the 3D structure of fuel cell electrodes. It was demonstrated that the electrode processing significantly affects pore size, pore distribution, and tortuosity. This method and result is particular interesting for the development of FC, RFB, and LiB electrodes in the future, as controlled electrode structuring and the utilization of oxidic supports in FC become more and more important.

We present the applicability of X-ray Raman Spectroscopy of light
elements and high energy resolution fluorescence detection XAS to
probe the electronic structure of energy storage materials under
in-situ conditions. In particular, recent advances in resolution and
throughput of x-ray raman spectroscopy (XRS) offer the capability to
measure, with true bulk sensitivity (10s um to mm probing depth), 1s
x-ray absorption profiles of light elements and L edges of transition
metals with less than 0.3eV resolution. Initial results from the
Spectroscopy program at SSRL and resulting from collaborations with
groups in various energy storage fields will be presented.

Conventional nickel-based anodes of solid oxide fuel cells degrade when exposed to hydrocarbon fuels due to the coking on the nickel surface. Several surface modification materials can help nickel resist coking, including BaO, BaZrO₃, and BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3-d. To rationally tailor anode materials for better stability, it is crucial to understand the mechanism of coking resistnace. This study used Raman spectroscopy to monitor SOFC anode materials under propane exposure at high temperatures. A time-resolved analysis of carbon formation was used to assess the propensity for coking of different anode materials. For example, a BaO-Ni mixture showed much less carbon deposition than plain Ni in the presence of propane. Using in-situ Raman to monitor BaO under this condition revealed the conversion of -OH into -CO₃, providing important insight into coking resistance. To increase the detection sensitivity of surface species, Ag nanoparticles enclosed by SiO₂ shells were applied onto nickel substrates to provide surface enhanced Raman scattering (SERS), which significantly enhanced the signal from carbon deposited on nickel surfaces.

Lowering the overpotential required to drive the oxygen evolution reaction (OER) is critical for the development of efficient solar fuels devices. NiOx is known as the best earth-abundant metal oxide catalyst for OER in alkaline media. The addition of rare earth elements to NiOx has shown the enhancement of the catalytic activity of OER owing to the formation of perovskite structure. However, the high temperature annealing required for the formation of perovskite structure limits the application of such catalysts. In this presentation, we&’ll report a study on electrodeposited NiOx thin films with the incorporation of rare earth elements. The study shows the rare earth elements have a promotion effect of NiOx on OER catalytic activity without the formation of perovskite structure.
The structure and surface species of these oxide films are essential for understanding the mechanism and the development of better electrocatalysts. In alkaline solution, a layer of Ni(OH)2 is formed immediately and then transformed to NiOOH when a positive potential is applied. Both Ni(OH)2 and NiOOH have different structures related to the OER activity. It&’s widely accepted in the literature that the β-type is the active form for catalysis of the OER. The structural differences of these phases gives rise to the variation of the Ni-O lattice modes, which can be distinguished via Raman or IR spectroscopy at frequencies between 400 and 700 cm-1. It's evident in our in-situ Raman study that at the potential where the OER occurs, the β-NiOOH phase related Ni-O vibration was observed on rare earth metal-doped NiOx, while a γ-phase was seen on NiOx film. The results demonstrate the power of the in-situ Raman spectroscopy on the mechanistic understanding of such promotion effect in combined with SEM and electrochemical rotation disk studies.

A combination of real-time Raman spectroscopy, optical imaging, and optical reflectivity are described to characterize and control the growth kinetics of graphene and carbon nanotubes. In both materials, the key parameters relevant to energy applications - defects, nucleation density, size / length, number of layers - depend critically on the growth mechanisms and kinetics. However, very few in situ characterization studies have been performed to understand the nucleation and growth kinetics of these important materials under typical growth conditions. For graphene growth on Ni, fundamental synthesis questions are addressed including the timescales for rapid nucleation and growth and whether growth occurs at high temperature or upon cooldown for metals which dissolve carbon. For aligned arrays of single-wall carbon nanotubes (SWNTs) grown on Fe, the density and diameter distribution of the nanotubes in the array are highly dependent upon the flux of feedstock gas.
In both cases, to understand the rapid nucleation and growth kinetics, pulsed valves are used to “digitally” supply ~ 0.2-s acetylene gas pulses of known flux to substrates. For SWNT arrays, time-resolved interferometry and absorption are used to simultaneously measure the length increase and the density of the arrays for each gas pulse. The density of the arrays is shown to be highly flux dependent, with high fluxes extinguishing the growth of small-diameter nanotubes. This effect is discussed in terms of autocatalytic kinetics.[1] By controlling the flux, it is shown that extremely short SWNT arrays can be grown incrementally, with real-time monitoring of length ± 20 nm. [2] For graphene growth, Raman spectroscopy with 1-s temporal resolution is used to complement the reflectivity and imaging studies in order to simultaneously characterize the characteristic G and 2D bands in situ during growth. High quality single and multilayered graphene is found to grow rapidly at high temperatures (800-850C) with different fractions precipitating upon cooldown depending on the acetylene flux. These real-time diagnostics are applicable not only for SWNT and graphene growth, but for the growth, characterization, and processing of other aligned nanorods and 2D materials currently being explored for energy applications.
Research supported by the U.S. Department of Energy, Basic Energy Sciences, Materials Science and Engineering Division, and performed in part at the 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, U.S. Department of Energy.
[1] Geohegan, D. B., Puretzky, A. A., et al., ACS Nano 5, 8311 (2011).
[2] Puretzky, A. A., Geohegan, D. B., et al., Small 8(10), 1534 (2012).

To help improve the functioning of nano Si based lithium ion batteries (LIBs) [1] numerous in situ studies have been recently reported using in situ XRD and in situ TEM studies. They highlight that during the first lithiation, crystalline-Si (c-Si) is converted into an amorphous-Li-silicide phase (a-LixSi) that transforms into crystalline-Li-silicides (c-LixSi), typically c-Li15Si4 at a low potentials. Amorphous-Si (a-Si) is then formed on charge. For all subsequent cycles, a-LixSi is a dominant component in the working potential range, but its composition and structure varies with state of charge. Furthermore, its interplay with c-Li15Si4 and/or Li15+δSi4 phases at the low voltage could have a critical role in the capacity loss process. Therefore, it is of great importance to monitor a-LixSi formation over multiple cycles as well as c-LixSi under practical operating conditions; since the major phases are amorphous, this requires the use of structural probes of local order. In situ 7Li nuclear magnetic resonance (NMR) is another powerful method to monitor both amorphous and crystalline phase formation upon lithiation-delithiation, even if they the phases are transient (metastable). Our previous work [2] studied the initial discharge of a micron-Si-carbon composite by in situ NMR spectroscopy, but focused only on the 1st cycle. However, further in situ NMR studies over multiple cycles are essential for understanding the phase evolution and further improvement. Here, we employ Si nanowires as a model system to study the structural modifications over multiple cycles for the first time by in situ NMR spectroscopy. The work is accompanied by a systematic ex situ electrochemical study.
[1] Chan, C. K.,Peng, H. L.,Liu, G.,McIlwrath, K.,Zhang, X. F.,Huggins, R. A.and Cui, Y. 2008 Nat Nanotechnol 3 31
[2] Key, B.,Bhattacharyya, R.,Morcrette, M.,Seznec, V.,Tarascon, J. M.and Grey, C. P. 2009 J. Am. Chem. Soc. 131 9239

Many oxide electronic thin films grown on SrTiO₃ and BaSrTiO₃ exhibit properties that derive from atomic-scale interactions at their interfaces, yet direct measurement of the electronic states at these interfaces under different growth and processing conditions is needed to understand fully the physical mechanisms involved. We used depth resolved cathodoluminescence spectroscopy (DRCLS) [1] to measure localized electronic states of native point defects at SrTiO₃ and BaSrTiO₃ interfaces on a nanometer (nm) scale. DRCLS&’s interface-specific capability reveals the segregation of these electrically-active sites to surfaces and interfaces for a wide range of oxides. Besides Schottky barriers, DRCLS can now correlate native point defects with thermal conductivity, RF dielectric properties such as permittivity and loss, and native point defects as they form inside operating sub-micron transistors. Based on a matrix of 100 nm Sr_xTiO_3+δ (0.95< x <1.05) thin films grown by molecular beam epitaxy (MBE) on substrates with -0.9 to +1.2% lattice mismatch, oxygen vacancies V_O and Ti³⁺ charge states within nms of the interfaces vary systematically with stoichiometry, oxygen pressure P(O₂), growth temperature T, and lattice mismatch strain. With increasing T and decreasing P(O₂), V_O defects and their complexes increase. With increasing compressive strain, Ti³⁺ defects decrease due to cation - cation repulsion. Thermal conductivity Λ exhibits a clear trend with increasing V₀ density vs. no correlation with Ti³⁺ . DRCLS reveals pronounced correlations of Ti³⁺ with RF dielectric permittivity vs. V_O density with loss, tan(δ). MBE-grown Ba_xSr_1-xTiO₃ (x=1, 0.5, 0) / SrTiO₃ heterojunctions exhibit optical emissions that DRCLS identifies with V_O,Ti³⁺, and Ba vacancies V_Ba in different charge states, with tan(δ) decreasing as V_Ba increases. We also grew stoichiometric 20 - 100 nm BaTiO₃ and Ba_0.5Sr_0.5TiO₃ epilayers by MBE without supplying oxygen during growth. XPS depth profiles show that oxygen diffuses out of the SrTiO₃ substrates during growth, resulting in DRCLS V_O densities increasing dramatically within tens of nm below the BaSrTiO₃ / SrTiO₃ interfaces vs. decreasing P(O₂). DRCLS also reveals striking V_O - related complex decreases within 2-3 nm of free SrTiO₃surfaces with extrinsic tensile strain, demonstrating the ability to rearrange defects on a nm scale by applying mechanical forces, even at room temperature. Together, these results emphasize that electrically-active native point defects can vary by orders of magnitude near oxide electronic interfaces with densities that correlate strongly with a range of macroscopic physical properties. Furthermore, the DRCLS technique provides evidence that these defect species can be controlled by combinations of MBE growth temperature, pressure, stoichiometry, and strain.
1. L. J. Brillson, “Applications of Depth-Resolved Cathodoluminescence Spectroscopy,” J. Phys. D: Appl. Phys. 45, 183001 (2012)

As novel electrolytes and porous electrodes are developed for a new generation of supercapacitors, it becomes more important to understand the transport of ions in and out of pores under different cycling conditions. This behavior becomes especially critical when the pore diameter matches the ion size, as the presence of a superionic state and consequent ion swapping results in significantly higher charge storage densities. While this behavior has been modeled and indirectly observed using electrochemical techniques, the exact ion behavior under those conditions, and the appropriate diffusion limitations, have not been fully characterized and understood. In our work, we present an in situ method for correlating electrochemical data from cyclic voltammetry, galvanostatic cycling, impedance spectroscopy, and square wave voltammetry with infrared intensity signals obtained from functional groups on electrolyte ions. The analysis is accomplished with a new experimental technique that combines electrochemical techniques with attenuated total reflectance (ATR) infrared (IR) spectroscopy to investigate entire functioning capacitors at the electrode/ATR interface. This technique demonstrates the capability of FTIR spectroscopy to selectively and simultaneously measure changes in the individual cation and anion dynamics of the electrolyte. For the active material, carbide-derived carbons (CDCs) with a 30 nm average particle size, that feature high surface areas and a microporous pore structure, were synthesized. A 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI) neat ionic liquid was used to perform electrochemical testing in two and three-electrode configurations. A 50 nm-thick gold foil was deposited on the carbon surface to facilitate IR spectrum collection, simultaneously acting as a current collector. We were able to correlate IR-detected ion mobility with current-voltage response, further supporting the feasibility of the use of ATR-IR spectroscopy technique to assess the dynamics of ion transport in and out of subnanometer pores.

Positron annihilation spectroscopy is a method sensitive to neutral and negatively charged open volume defects. The decreased electron density in a vacancy manifests itself as an increase of positron lifetime and the narrowing of the 511 keV photo-peak in the annihilation gamma spectrum, compared to a defect-free crystal. Positron lifetime spectroscopy provides information on the atomic structure, the charge state and often the concentration of the vacancies while the Doppler broadening of the photopeak allows the identification of atoms surrounding the vacancy defects. Positron annihilation spectroscopy has been efficiently used to identify and quantify technologically important vacancy-related defects in, for example, III-nitrides [1] and ZnO [2].
We present developments leading to the possibility of studying interfaces at the nanoscale in semiconductors and metal-oxide systems. The theoretical basis for these developments has already been set [3], while the necessary experimental steps are only now being taken. The combination of utilizing state-of-the-art slow positron beam technology together with pump-probe illumination and bias application to layered structures provides new possibilities in the identification of the origin of the positron signal and the charge transfer processes [4] at defects and interfaces. We present results obtained with these methods in opto-electronic semiconductor devices, inorganic and organic semiconductors for photovoltaic applications and oxidized metal surfaces.
[1] C. Rauch, I. Makkonen, and F. Tuomisto, Phys. Rev. B 84, 125201 (2011).
[2] Y. Dong, F. Tuomisto, B. G. Svensson, A. Yu. Kuznetsov, and L. J. Brillson, Phys. Rev. B 81, 081201(R) (2010).
[3] I. Makkonen, A. Snicker, M. J. Puska, J.-M. Mäki, and F. Tuomisto, Phys. Rev. B 82, 041307(R) (2010).
[4] J.-M. Mäki, F. Tuomisto, A. Varpula, D. Fisher, R. U. A. Khan, and P. M. Martineau, Phys. Rev. Lett. 107, 217403 (2011).