Charge Redistribution of Co₉S₈/MoS₂ Heterojunction Microsphere Enhances Electrocatalytic Hydrogen Evolution

The electrocatalytic hydrogen evolution activity of transition metal sulfide heterojunctions are significantly increased when compared with that of a single component, but the mechanism behind the performance enhancement and the preparation of catalysts with specific morphologies still need to be explored. Here, we prepared a Co₉S₈/MoS₂ heterojunction with microsphere morphology consisting of thin nanosheets using a facile two-step method. There is electron transfer between the Co₉S₈ and MoS₂ of the heterojunction, thus realizing the redistribution of charge. After the formation of the heterojunction, the density of states near the Fermi surface increases, the d-band center of the transition metal moves downward, and the adsorption of both water molecules and hydrogen by the catalyst are optimized. As a result, the overpotential of Co₉S₈/MoS₂ is superior to that of most relevant electrocatalysts reported in the literature. This work provides insight into the synergistic mechanisms of heterojunctions and their morphological regulation.