Thiomolybdate-Based Active Molecular Mimics of MoS2 Edge for Efficient Hydrogen Evolution Reaction

Abstract

Electrocatalytic hydrogen production via water electrolysis is an environmentally-benign energy technolology that is a key element of hydrogen-based energy cycles. To enhance overall efficiency of the water electrolysis, the development of electrocatalysts with high activity and durability is of prime importance. As an alternative to expensive precious metal catalysts, molybdenum sulfides have received great attention as the hydrogen evolution reaction (HER) catalysts. Among various strategies enhancing their catalytic activities, design of molecular mimics for active MoS2 edges has achieved significant turnover frequency by exposing high density of the active sites. In this work, we report that even the smallest, commercially available molecular compound, monomeric thiomolybdate (MoS42−) can catalyze the HER with very high efficiency, comparable to the state-of-the-art nanostructured MoSx-based HER catalysts. Its unexpectedly high HER activity could be attributed to condensation of S2− ligands in MoS42− anions, generating active sulfur sites. In addition, its activity and durability were further improved when adhered onto Au nanocrystals (NCs). Strong physical adhesion between MoS42− and Au NCs as well as electronic communication between them could improve the activity and durability of the resulting catalyst in strongly acidic electrolyte.