Enhancing hydrogen evolution on the basal plane of transition metal dichacolgenide van der Waals heterostructures

Recent years have seen a surge in the use of low-dimensional transition metal dichacolgenides, such as MoS₂, as catalysts for the electrochemical hydrogen evolution reaction. In particular, sulfur vacancies in MoS₂ can activate the inert basal plane, but that requires an unrealistically high defect concentration (~9%) to achieve optimal activity. In this work, we demonstrate by first-principles calculations that assembling van der Waals heterostructures can enhance the catalytic activity of MoS₂ with low concentrations of sulfur vacancies. We integrate MoS₂ with various two-dimensional nanostructures, including graphene, h-BN, phosphorene, transition metal dichacolgenides, MXenes, and their derivatives, aiming to fine-tune the free energy of atomic hydrogen adsorption. Remarkably, an optimal free energy can be achieved for a low sulfur vacancy concentration of ~2.5% in the MoS₂/MXene-OH heterostructure, as well as high porosity and tunability. These results demonstrate the potential of combining two-dimensional van der Waals assembly with defect engineering for efficient hydrogen production.