Tuning Interfacial Active Sites over Porous Mo2N‑Supported Cobalt Sulfides for Efficient Hydrogen Evolution Reactions in Acid and Alkaline Electrolytes

Although various cobalt-sulfide-based materials have been reported for the hydrogen evolution reaction, only a few have achieved high activity in both acid and alkaline electrolytes due to the inherent poor conductivity and low active sites. In this work, a heterojunction of cobalt sulfide and Mo2N is designed for efficient hydrogen evolution reactions in both acid and alkaline electrolytes. X-ray photoelectron spectroscopy reveals that Mo–S bonds are formed at the interface between Mo2N and CoS2, which result in the fabricated Mo2N/CoS2 materials exhibiting a considerably enhanced hydrogen evolution reaction activity than the corresponding Mo2N, CoS2, and most reported Mo- and Co-based catalysts in electrolytes of H2SO4 and KOH solutions. Density functional theory calculations suggest that the redistribution of charges occurs at the heterointerface. In addition, the interfacial active sites possess a considerably lower hydrogen adsorption Gibbs free energy than those atoms that are far away from the interface, which is beneficial to the process of hydrogen evolution reaction. This study provides a feasible strategy for designing hetero-based electrocatalysts with a tuned highly active interface.