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-MoS_x) 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.

氢化物转移是许多经济和环境重要反应的关键，包括 H ₂释放和 NADH 再生。因此，氢化物的电化学生成可以推动化学反应的电气化，以提高其对绿色经济的可持续性。_{含钼催化剂最近被认为是最有希望的 H 2}析出非贵重催化剂之一，但钼赋予该活性的机制仍存在争议。在这里，我们展示了在无定形硫化钼 (a- ^MoS _x) 在析氢反应期间，并将其催化作用扩展到将生物重要的能量载体 NAD 选择性氢化为其活性 1,4-NADH 形式。此外，这种反应性适用于其他具有 HER 活性的硫化钼。我们的结果证明了钼在异质 H ₂演化中的直接作用。这一机理发现还表明，硫化钼具有作为生物催化中 NADH 再生的经济电催化剂的潜力。