Graduate Research Assistant, Washington University in St. Louis
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“Design of 2D transition metal dichalcogenide alloys for electrocatalysis”
Electrocatalysts are a crucial component in many clean energy technologies such as batteries, fuel cells, and CO2 converters. Currently, expensive noble metals are used as the commercial standard for electrocatalysis, motivating a search for a new class of inexpensive materials with competitive electrocatalytic properties. Layered transition metal dichalcogenides (TMDCs) have demonstrated impressive catalytic activity in several electrochemical systems including in Li-air batteries and for CO2 reduction. However, outside of group VI TMDCs, the miscibility of TMDC alloys remains largely unknown. Furthermore, the usage of multiple principal elements to form so-called high entropy alloys (HEAs) of TMDCs has not been previously explored. Motivated by the potential to use alloying to further improve the catalytic applications of TMDCs, we used first-principles calculations to perform a comprehensive analysis of the stability of 25 quasi-binary transition metal- and chalcogen-site TMDC alloys and a select number of 4- and 5-component transition metal-site TMDC HEAs. We verified our stability predictions through the successful synthesis of many TMDC alloys, including new group V quasi-binary alloys and the first ever high entropy TMDC alloys. For CO2 reduction, the quasi-binary alloy Nb0.5Ta0.5S2 and HEA (MoWVNbTa)0.2S2 demonstrated fast conversion rates and high energy efficiency. As part of a Li-air battery, Nb0.5Ta0.5S2 showed high efficiency and reliable cycle stability. First-principles calculations were used to elucidate the reasons for high catalytic activity in CO2 reduction: a combination of optimized catalyst-site bonding energy and the facilitation of site-hopping through alloying.
Acknowledgements: This work was supported by National Science Foundation (NSF) through DMREF-1729787.
John Cavin, Graduate Research Assistant, Washington University in St. Louis
John Cavin is a physics Ph.D. student at Washington University in St. Louis. He is working with professor Rohan Mishra and plans to graduate in Summer 2021. His research interests include computational and theoretical materials science and condensed matter physics with a focus on catalysis and 2D materials.