LAUSR

Abstract In this paper, the mechanisms of H2 evolution over the Mo-Edge of 2H-MoS2 with the unsaturated Mo (MoU) and S (SU) were investigated by the density functional theory. The calculations indicated that MoU was a key active site for H2 evolution. In the process of H2 evolution, the SU firstly absorbed H atom by the Volmer reaction, which caused the aggregation of electron on MoU, resulting in the barriers reduction of H transfer and H2 evolution on MoU. The formation of molybdenum hydride was the rate-limiting step. Compared to Mo-edge in 2H-MoS2, the barrier of key step for H2 evolution on Mo-edge with SU and MoU decreased obviously. This implied that the removal fractional S from the Mo-edge of 2H-MoS2 could enhance its H2 evolution activity and the electron trapping ability of active site for H2 evolution by the Volmer-Heyrovsky reaction might affect its activity.