Ag₂S-Modified ZnIn₂S₄ Nanosheets for Photocatalytic H₂ Generation

Ag2S was successfully deposited on ZnIn2S4 (ZIS) nanosheets via a room temperature cation exchange reaction. The facile synthetic strategy allows Ag2S to easily form atomic-level intimate contact with ZIS nanosheets, which ensures efficient interfacial charge transfer. With the optimal deposition ratio (1.10 mol %), the hydrogen evolution rate of 25 mg Ag2S-modified ZIS nanosheets is 25.02 μmol h–1, which is 2.3 times higher than that of pristine one. It was also found that partial Ag2S was reduced to metallic Ag during the photocatalytic reaction. On the basis of the experimental results, the photocatalytic reduction mechanism was discussed. Under light irradiation, metallic Ag can rapidly capture photogenerated electrons from ZIS nanosheets and transfer electrons to the active sites on Ag2S. As a result, the synergistic effect of Ag2S and metallic Ag leads to a higher photocatalytic hydrogen evolution activity. This work offers an improved understanding of the reaction mechanism of cation exchange in ternary sulfide and provides an opportunity to develop a highly efficient photocatalyst using an Ag2S-based cocatalyst.