Anion–Cation Double Substitution in Transition Metal Dichalcogenide to Accelerate Water Dissociation Kinetic for Electrocatalysis

Until now, many works have shown that the hydrogen evolution reaction (HER) performance can be improved by anion or cation substitution into the crystal lattice of pyrite-structure materials. However, the synergistic effects of anion–cation double substitution for overall enhancement of the catalytic activity remains questionable. Here, the simultaneous incorporation of vanadium and phosphorus into the CoS₂ moiety for preparing 3D mesoporous cubic pyrite-metal Co_1-xV_xSP is presented. It is demonstrated that the higher catalytic activity of CoS₂ after V incorporation can be primarily attributed to abundance active sites, whereas P substitution is responsible for improving HER kinetics and intrinsic catalyst. Interestingly, due to the synergistic effect of P–V double substitution, the 3D Co_1-xV_xSP shows superior electrocatalysis toward the HER with a very small overpotential of 55 mV at 10 mA cm⁻², a small Tafel slope of 50 mV dec⁻¹, and a high turnover frequency of 0.45 H₂ s⁻¹ at 10 mA cm⁻², which is very close to commercial 20% Pt/C. Density functional theory calculation reveals that the superior catalytic activity of the 3D Co_1-xV_xSP is contributed by the reduced kinetic energy barrier of rate-determining HER step as well as the promotion of the desorption H₂ gas process.