Importance of Mo oxidation state for efficient HER electrocatalysis: A DFT perspective to validate experiments

Designing effective, stable and cheap materials for hydrogen evolution reaction (HER) through water electrolysis could have a substantial impact on renewable energy technologies. Up to date expensive and rare metals are the most effective and benchmarks catalysts for HER, which limits their widespread use. Enormous efforts dedicated to the development of non-noble and efficient electrocatalysts for water splitting are required to tackle this problem. This has encouraged our present work where we have designed and investigated HER on an extensive range of Mo catalysts. We propose a unified designing criterion for Mo based HER catalysts based on evidences from electrochemical, physical, functional, and computational approaches on a wide range of Mo-based catalysts. We show that Mo-based HER catalysts may evolve H₂ through a common pathway centered on the formation of a hydride and the underlying principle of Mo catalyst activity is the presence of the Mo³⁺ oxidation state.