Activating the MoS Basal Planes for Electrocatalytic Hydrogen Evolution by 2H/1T' Structural Interfaces.

Exploring highly efficient catalysts for the electrochemical hydrogen evolution reaction (HER) is highly demanded in the sustainable production of hydrogen. MoS is recognized as a potential candidate catalyst for HER, but its active site is mainly located at the edges, which is extremely limited. Here, we have investigated the catalytic performance of HER in the MoS basal planes during the structural transition from the 2H to the 1T' phase. Different kinds of 2H/1T' structural interfaces are considered, and the adsorbed H free energies (Δ) on these surfaces were calculated. The active site for H adsorption is on the top of S atoms at the 2H/1T' phase boundary. The zigzag 2H/1T' interfaces exhibit an optimal performance for the Volmer reaction with the Δ being very close to zero. The Volmer-Heyrovsky reaction is dominantly preferred to the Volmer-Tafel reaction. Our study provides a new picture to boost up the active sites of the basal plane for HER on MoS, and this electrocatalytic mechanism is also applicable for other transition metal dichalcogenide materials.