Excited electron dynamics in the interface of 2H-1T hetero-phases of monolayer MoS 2 : time-dependent density functional theory study

Monolayer MoS2 usually exhibits two distinct phases (2H and 1T) at room temperature. The 2H phase, which is thermodynamically more stable with a direct bandgap of about 2.4 eV, can be utilized as a hydrogen evolution reaction (HER) catalyst owing to its unique photovoltaic and photo-catalytic natures. In this study, we investigate the geometric and the electronic structures at the boundary of the two phases of MoS2, and we find that the excited carrier dynamics at the boundary can lead to far enhanced catalytic activity. By performing real-time time-dependent density functional theory calculations, we identified that the excited electrons in the 2H phase region are transferred and accumulated in the 1T phase region, leading to a charging of the 1T phase region. Thus, surplus charge sharply decreases the dissociation barrier of the adsorbed oxygen molecule, providing a remarkable catalytic nature for the oxygen reduction reaction energy (ORR). We compared the thermodynamics profile of the ORR with that on a platinum (100) surface. We suggest that the MoS2 heterophase boundary can serve as a novel photocatalyst.