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 Δ G 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. Image 1 • A near-zero hydrogen adsorption free energy of CoMoP is realized. • Electrons transfer results in middle d band center of CoMoP. • CoMoP in lower valence states enhances the stability and catalytic activity. • Excellent stability at a high current density of 370 mA cm−2. [ABSTRACT FROM AUTHOR]