Tuning of metallic valence in CoMoP for promoting electrocatalytic hydrogen evolution

CoMoP_x-based electrocatalysts are promising for hydrogen evolution reaction (HER) but suffer from high overpotential and poor stability at large current density. Herein, we propose CoMoP@NF in lower valence states by thorough phosphorization which improves the adhesion of the catalysts on substrate and facilitates the Volmer step. The CoMoP@NF can reach 39 mV at 10 mA cm⁻², 119 mV at 100 mA cm⁻², and a low Tafel slope of 73.3 mV per decade. The decline of i-t test in 10 h at ~370 mA cm⁻² is only 1 mA cm⁻². Theoretical calculations confirm the rational design of CoMoP whose ΔG_H∗ is as low as 0.15 and −0.01 eV corresponding to (013) and (211) facets, respectively. Electrons transfer from Co to Mo results in middle d band center of CoMoP that promotes H adsorption and desorption. This concept could provide valuable insights into the design of other catalysts for HER and beyond.