Project 10: Understanding the Fundamentals of Hydrogen Evolution in Earth Abundant Catalysts (Prof. Gautam Gupta, IE)

Project Description: Hydrogen is an ideal fuel for sustainable energy. More than 90 % of hydrogen   production is currently obtained by reforming of fossil fuels or using expensive semiconductor based solar cells in combination with expensive catalyst (Pt).(1) Recently, 2D layered materials especially Transition metal chalcogenides (TMDs) have revealed promising HER catalytic activity and opto-electronic properties. Briefly, TMDs are earth abundant layered materials, with chemical formula MX2 where M is a transition metal from group IV, V or VI and X is a chalcogen (S, Se, or Te) e.g. MoS2 (Fig. 1). Bulk MoS2 powders have limited catalytic activity due to an inert crystal basal plane, stacked sheets, and low in-plane conductivity.(2

The Problem: Despite several advances in enhancing the electrocatalytic activity of TMDs, the overpotential is relatively high as compared to that of Pt and durability remains a concern. Further enhancement in catalytic performance is precluded due to our lack of understanding of how the crystal structure, morphology and electronic conductivity are correlated to the electrocatalytic activity.

Preliminary Results: Our most recent studies in field of catalysis suggest that phase transformation, doping, conductivity and solvent interactions may play an important role in enhancing the catalytic activity of materials. (3-6)(Nature Comm. 2016, Science Advances 2016, Nature Materials 2016, and JPCC 2015, Nature Materials 2014)

Research Approach: The student will work on elucidating the role of crystallinity, microstructure and d-spacing on figures of merit in electrocatalytic activity. Week 1. The student will be provided with synthesized TMDs WS2 and MoS2.  The synthesized materials will be subjected to (a) control the d-spacing of the 2D sheets in transition metal dichalcogenides by utilizing solvents based on Hansen’s solubility parameter (5)  to ensure proton diffusion and reaction at each basal plane (Week 2-3)  (b) enhance conductivity of the catalysts by intercalation of monovalent or divalent cations (Week 4)  (c) CVD grown single layer to a few layer TMDs will be subjected to electrical measurements  (four-probe and single flake electro catalysis at Micro/Nano Technology and Engineering center, in Week 5-8) to understand the effect of doping and solvent interaction at a micro scale. The student will utilize the standard concepts in microfabrication to obtain devices for electro catalysis. The fundamental properties obtained will dictate the experimental approach to obtain bulk catalysts using hydrothermal approach. (Week 9-10) The student will develop a poster and will be a critical part of the publication resulting from the work.

References:

 

1.         W. Sheng, H. a. Gasteiger, Y. Shao-Horn, Hydrogen Oxidation and Evolution Reaction Kinetics on Platinum: Acid vs Alkaline Electrolytes. Journal of The Electrochemical Society 157, B1529-B1529 (2010).

2.         R. R. Chianelli et al., The Reactivity of MoS2 Single-Crystal Edge Planes. Journal of Catalysis 92, 56-63 (1985).

3.         D. R. Cummins et al., Catalytic Activity in Lithium-Treated Core–Shell MoOx/MoS2 Nanowires. The Journal of Physical Chemistry C 119, 22908-22914 (2015).

4.         D. R. Cummins et al., Efficient hydrogen evolution in transition metal dichalcogenides via a simple one-step hydrazine reaction. Nat Commun 7,  (2016).

5.         U. Martinez et al., Critical role of intercalated water for electrocatalytically active nitrogen-doped graphitic systems. Science Advances 2,  (2016).

6.         D. Voiry et al., The role of electronic coupling between substrate and 2D MoS2 nanosheets in electrocatalytic production of hydrogen. Nature materials,  (2016).