Scalable Synthesis of Large 2D Transition Metal Layered Hydroxides

When and Where

Nov 28, 2022
10:30am - 10:45am

Hynes, Level 2, Room 207

Presenter

Lu Ping

Gillian Minarik

Hongze Gao

Xi Ling

Co-Author(s)

Lu Ping¹,Gillian Minarik¹,Hongze Gao¹,Xi Ling¹

Boston University¹

Abstract

Lu Ping¹,Gillian Minarik¹,Hongze Gao¹,Xi Ling¹

Boston University¹

The first successful exfoliation of graphene1 in 2004 sparked a dramatic increase in 2D materials research and the repertoire of 2D materials family has since expanded. 2D crystals composed of single or few atomic layers display unique chemical, optical, and electronic properties compared with their bulk 3D counterparts due to the quantum confinement effect at the 2D limit2. Two–dimensional (2D) transition metal layered hydroxides (TM–LHs), a class of materials composed of transition metal centers sandwiched between layers of coordinating hydroxide anions have attracted considerable interest for their potential in developing clean energy source3,4 and storage technologies5,6. However, 2D TM–LHs with desired large domain size for electronic devices are not achieved yet, owing to challenges in reproducibility of 2D morphology and long-range crystallinity, limiting the domain size of previously reported samples (<5 μm)7,8. Here, we report repeatable synthesis of 2D α–Ni(OH)2 crystals of lateral size ∼20 μm with ∼8 atomic layers derived from a condition-controlled hydrothermal process. A detailed investigation on the influence of the most critical synthetic conditions, including soaking temperature, starting pH, and cooling rate, on the domain size, crystal phase, and morphology was performed, providing mechanistic insights into the formation of 2D α–Ni(OH)2 under hydrothermal reaction conditions. Moreover, the optical band gap energy of the synthesized 2D Ni(OH)2 flakes is extrapolated as 2.55 eV from optical absorption measurements, suggesting the insulating nature. Electrical measurements further confirmed the insulating nature of the synthesized flakes, and a dielectric strength of up to 3.2 MV/cm was collected on a 4.9 nm flake (∼6 atomic layers), which makes it a promising candidate for gate dielectric materials for 2D FETs devices. Furthermore, the crystal fields and orientations of 3d transition metals were compared and analyzed to evaluate the applicability of this method to other 3d first–row TM–LHs. 2D Co(OH)2 was successfully synthesized following the same pathway, promoting the hydrothermal method as a facile, generalizable method for large–scale preparation of 2D TM–LHs. This work demonstrates a scalable pathway to synthesize large 2D TM–LHs flakes from simple methods and paves the way for the fundamental physical properties study and device applications of the 2D TM–LHs. Reference 1. Novoselov, K. S. et al. Two-dimensional atomic crystals. Proc. Natl. Acad. Sci. U. S. A. 102, 10451–10453 (2005). 2. Tan, J., Li, S., Liu, B. & Cheng, H.-M. Structure, Preparation, and Applications of 2D Material–Based Metal–Semiconductor Heterostructures. Small Struct. 2, 2000093 (2021). 3. Deng, J., Wu, F., Gao, S., Dionysiou, D. D. & Huang, L.-Z. Self-activated Ni(OH)2 Cathode for Complete Electrochemical Reduction of Trichloroethylene to Ethane in Low-conductivity Groundwater. Appl. Catal. B Environ. 309, 121258 (2022). 4. Patil, S. J. et al. Fluorine Engineered Self-Supported Ultrathin 2D Nickel Hydroxide Nanosheets as Highly Robust and Stable Bifunctional Electrocatalysts for Oxygen Evolution and Urea Oxidation Reactions. Small 18, (2022). 5. Huang, Z. H. et al. An electro-activated bimetallic zinc-nickel hydroxide cathode for supercapacitor with super-long 140,000 cycle durability. Nano Energy 82, 105727 (2021). 6. Wu, Y. et al. Rational design of cobalt–nickel double hydroxides for flexible asymmetric supercapacitor with improved electrochemical performance. J. Colloid Interface Sci. 581, 455–464 (2021). 7. Yuan, S. et al. Tunable metal hydroxide–organic frameworks for catalysing oxygen evolution. Nat. Mater. 21, (2022). 8. Liu, C., Bai, Y., Wang, J., Qiu, Z. & Pang, H. Controllable synthesis of ultrathin layered transition metal hydroxide/zeolitic imidazolate framework-67 hybrid nanosheets for high-performance supercapacitors. J. Mater. Chem. A 9, 11201–11209 (2021).