Mechanism of Hydrogen Evolution Reaction on 1T MoS2 from First Principles
The 1T phase of transition metal dichalcogenides (TMDs) has been demonstrated in recent experiments to display excellent catalytic activity for hydrogen evolution reaction (HER) but the catalytic mechanism has not been elucidated so far. Herein, using 1T MoS2 as the prototypical TMD material, we studied the HER activity on its basal plane from periodic density functional theory (DFT) calculations. Compared to the nonreactive basal plane of 2H phase MoS2, the catalytic activity of the basal plane of 1T phase MoS2 mainly arises from its affinity for binding H at the surface S sites. Using the binding free energy (DGH) of H as the descriptor, we found that the optimum evolution of H2 will proceed at surface H coverage of 12.5% 25% Within this coverage, we examined the reaction energy and barrier for the three elementary steps of the HER process. The Volmer step was found to be facile, whereas the subsequent Heyrovsky reaction is kinetically more favorable than the Tafel reaction. Our results suggest that.