Mo-dopant-strengthened basal-plane activity in VS2 for accelerating hydrogen evolution reaction

We report the basal-plane catalytic reactivity of VS2 can be significantly enhanced by Mo doping for hydrogen evolution reaction (HER). Our optimal experiments reveal that the Tafel slope and overpotential at -10 mA cm(-2) of VS2 are reduced by 82.8% and 73.6% respectively after the Mo doping. Furthermore, the turnover frequency at 300 mV and electrochemical surface area of the optimal Mo-doped VS2 exhibit 19.2- and 27.2-fold enhancements compared with the pure VS2, together with significantly improved long-term cycle stability. Our density functional theory (DFT) calculations suggest that Mo dopant reduces the hydrogen adsorption free energy on S sites, and consequently strengthens the basal-plane activity. We uncover a charge transfer mechanism from Mo to the outer surface of S atoms, leading to the enhancement of p-orbital density of states of S at Fermi level and thus far super HER performance. Our findings provide a promising route and theoretical framework to improve the electrocatalytic HER performance of VS2, and may have general implications to other transition metal disulfides.