Heterostructure CoMoO4–Co2Mo3O8 with valence-rich molybdenum for high-performance hydrogen evolution reaction in alkaline solution

Hydrogen evolution reaction (HER) is a promising clean and renewable energy strategy. Thus, efficient and inexpensive electrocatalysts for HER have attracted considerable attention. Here, we report a two-step method for the synthesis of a unique CoMoO4–Co2Mo3O8 heterostructure. The CoMoO4–Co2Mo3O8 heterostructure exhibited superior HER activity that included a low overpotential of 57 mV, a Tafel slope of 55 mV·dec-1 in a 1 M KOH solution, and excellent long-term stability given its high intrinsic activity and superior conductivity. Density functional theory calculations indicated that CoMoO4 and Co2Mo3O8 synergistically optimized electron distribution to reduce hydrogen adsorption energy and significantly enhance electrocatalytic activity. Our work may provide novel ideas for improving the HER performance of valence-rich transition element oxides.