First-principles study of catalytic activity of W-doped cobalt phosphide toward the hydrogen evolution reaction

In this study, we investigated the hydrogen evolution reaction (HER) on the (101) facet of pristine and W-doped CoP using the density functional theory. Two types of Co atoms are identified on the catalyst surface: the Co atoms that present the higher d band center are marked as valid sites, whereas the others are marked as invalid sites owing to their weaker H adsorption ability. It is further revealed that W-doping can decrease the d band center of the surface Co atoms, which is beneficial for the HER; however the exposure to W weakens the desorption of H. To address the strong adsorption effect of W, the doping sites and dopant content are analyzed, and the results indicate that 8.4 wt% W doping at the invalid surface Co sites is preferred; moreover, the optimal W content increases to 16.8 wt% when W is inserted into the subsurface. The effect of W doping is weakened when the doping site is far away from the surface.