Activating Inert Basal Planes of MoS2 for Hydrogen Evolution Reaction through the Formation of Different Intrinsic Defects

Nanoscale molybdenum disulfide (MoS2) has attracted ever-growing interest as one of the most promising nonprecious catalysts for hydrogen evolution reaction (HER). However, the active sites of pristine MoS2 are located at the edges, leaving a large area of basal planes useless. Here, we systematically evaluate the capabilities of 16 kinds of structural defects including point defects (PDs) and grain boundaries (GBs) to activate the basal plane of MoS2 monolayer. Our first-principle calculations show that six types of defects (i.e., V-s, V-MoS3, Mo-S2 PDs; 4 vertical bar 8a, S bridge, and Mo-Mo bond GBs) can greatly improve the HER performance of the in-plane domains of MoS2. More importantly, V-s and Mo-S2 PDs and S bridge and 4 vertical bar 8a GBs exhibit outstanding activity in both Heyrovsky and Tafel reactions as well. Moreover, the different HER activities of defects are well-understood by an amendatory band-center model, which is applicable to a broad class of systems with localized defect states. Our study provides a comprehensive picture of the defect-engineered HER activities of a MoS2 monolayer and opens a new window for optimizing the HER activity of two-dimensional dichalcogenides for future hydrogen utilization.