Mo3+ hydride as the common origin of H2 evolution and selective NADH regeneration in molybdenum sulfide electrocatalysts

Hydride transfers are key to a number of economically and environmentally important reactions, including H2 evolution and NADH regeneration. The electrochemical generation of hydrides can therefore drive the electrification of chemical reactions to improve their sustainability for a green economy. Catalysts containing molybdenum have recently been recognized as among the most promising non-precious catalysts for H2 evolution, but the mechanism by which molybdenum confers this activity remains debated. Here we show the presence of trapped Mo3+ hydride in amorphous molybdenum sulfide (a-MoSx) during the hydrogen evolution reaction and extend its catalytic role to the selective hydrogenation of the biologically important energy carrier NAD to its active 1,4-NADH form. Furthermore, this reactivity applies to other HER-active molybdenum sulfides. Our results demonstrate a direct role for molybdenum in heterogeneous H2 evolution. This mechanistic finding also reveals that molybdenum sulfides have potential as economic electrocatalysts for NADH regeneration in biocatalysis. The electrochemical generation of reactive hydrides has the potential to drive the electrification of chemical reactions. Now, a modified electron paramagnetic resonance set-up is put forward to demonstrate the role of Mo3+ hydride in amorphous MoSx to catalyse both the hydrogen evolution reaction and electrochemical NADH regeneration.