Facile construction of a sulfur vacancy defect-decorated CoSx@In2S3 core/shell heterojunction for efficient visible-light-driven photocatalytic hydrogen evolution

Photoinduced electron-separation and -transport processes are two independent crucial factors for determining the efficiency of photocatalytic hydrogen production. Herein, a sulfur vacancy defect-decorated CoS_x@In₂S₃ (CoS_x@V_S-In₂S₃) core/shell heterojunction photocatalyst was synthesized via an in situ sulfidation method followed by a liquid-phase corrosion process. Photocatalytic hydrogen evolution experiments showed that the CoS_x@V_S-In₂S₃ nanohybrids delivered an attractive photocatalytic activity of 4.136 mmol h^-1 g^-1 under visible-light irradiation, which was 8.23 times higher than that of the pristine In₂S₃ samples. As expected, V_S could enhance the charge-separation efficiency of In₂S₃ through rearranging the electrons of the In₂S₃ basal plane, in addition to improving the electron-transfer efficiency, as visually verified by transient absorption spectroscopy. Mechanism studies based on density functional theory calculations confirmed that the In atoms adjacent to V_S played a key role in the translation, rotation, and transformation of electrons for water reduction. This scalable strategy focused on defect engineering paves a new avenue for the design and assembly of 2D core/shell heterostructures for efficient and robust water-splitting photocatalysts.