First-principles studies on interfacial electronic coupling and the bifunctional electrocatalytic mechanism of MoSe2/C heterojunctions.

Water electrolysis for hydrogen production is a key technology for renewable energy conversion and storage. MoSe2 exhibits great promise as a low-cost bifunctional electrocatalyst, but its intrinsically poor conductivity limits its practical application. Forming heterojunctions with highly conductive carbon materials is an effective strategy. Therefore, first-principles calculations were employed to construct and identify the thermodynamically most stable C-Se stacking configuration. Results revealed that interfacial coupling induces band rearrangement, rendering the system metallic. Meanwhile, it also creates an intrinsic electric field that accelerates charge transport and shifts the d-band center of the Mo active sites to optimize intermediate adsorption. Furthermore, the 55th Se vacancy was predicted to be the optimal active site, and the heterojunction was confirmed to significantly lower the energy barriers for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Guided by these predictions, the MoSe2/C/NF catalyst was synthesized in situ on a three-dimensional conductive nickel foam (NF) substrate. In a 1.0 mol L-1 KOH electrolyte, it exhibited substantially enhanced HER and OER activities compared to MoSe2/NF. This work systematically indicates the intrinsic correlation between the electronic coupling at the MoSe2/C interface and enhanced bifunctional catalytic performance.