Abstract: Driven by endless solar energy, photocatalytic H₂ evolution from water splitting and CO₂ conversion to hydrocarbon fuels over semiconductor photocatalysts are of great potential to simultaneously settle the greenhouse effect and energy shortage. Herein, Cr-doped zinc sulfide (ZnS) with accompanying sulphur vacancies (Vs) photocatalytic materials is developed by a facile hydrothermal method. The Cr dopants centralize photoinduced holes and Vs trap electrons, forming a synergistic effect for accelerating charge separation and transfer. The reaction energy barrier for both H₂ evolution and CO₂ reduction has been optimized. Therefore, in the absence of a cocatalyst, the optimal catalyst (Zn_0.94Cr_0.06S) achieves an outstanding H₂ evolution activity of 20.3 mmol g^-1 h^-1, which is approximately 2.9 times higher than 6.9 mmol g^-1 h^-1 for pristine ZnS. In addition, in the gas-solid reaction system without co-catalysts or sacrificial agents, the Zn_0.94Cr_0.06S exhibits a considerable CO evolution rate of 19.56 μmol g^-1 h^-1, about 10.1 times higher than ZnS (1.94 μmol g^-1 h^-1). Both the performances for H₂ evolution and CO₂ reduction of Zn_0.94Cr_0.06S outperform most of the previously reported photocatalysts. Particularly, the Zn_0.94Cr_0.06S possesses superior stability, the photoactivity of which exhibits no noticeable deactivation after six cycles' reactions. This work may shed light on the rational design and fabrication of highly efficient materials via combining individual element doping and defect engineering.

Key words: Photocatalysis, H₂ evolution, CO₂ reduction, Cr doping, Sulphur vacancy