CoMoPx-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 similar to 370 mA cm(-2) is only 1 mA cm(-2). Theoretical calculations confirm the rational design of CoMoP whose Delta 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. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.