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Semiconductor photocatalysis is a promising method for utilizing solar energy to decompose water and degrade pollutants. However, the limited visible light absorption capacity and high carrier complexation rate hinder the utilization of sunlight for photocatalysts. The study prepared V O BiOBr/V S ZnIn 2 S 4 S-scheme heterojunction photocatalysts with sulfur and oxygen vacancies using a two-step solvothermal method. The photocatalyst was then used to simulate sunlight decomposition of water for hydrogen production and degradation of dye wastewater. Characterisation tests revealed that the incorporation of sulfur and oxygen vacancies effectively enhanced the visible light absorption of BiOBr and ZnIn 2 S 4. The construction of S-scheme heterojunction resulted in an improvement in visible light absorption capacity, as well as the promotion of separation and migration of photogenerated carriers. The study demonstrates that V O BiOBr/V S ZnIn 2 S 4 exhibits superior hydrogen precipitation and degradation properties compared to BiOBr/ZnIn 2 S 4 without S and O vacancies and V S ZnIn 2 S 4 without a heterojunction when subjected to simulated sunlight irradiation. The results of the tests and mechanistic analyses suggest that the synergistic effect of S and O vacancies and heterojunction enhances the photocatalytic performance. This study offers novel perspectives on the production of multifunctional photocatalysts that effectively utilize sunlight. [Display omitted] • Novel dual vacancy V O BiOBr/V S ZnIn 2 S 4 heterojunctions were successfully constructed. • V O BiOBr/V S ZnIn 2 S 4 photocatalysts demonstrate high photocatalytic activity under simulated sunlight. • The synergistic effect of vacancy and heterojunction greatly enhances the photocatalytic performance of ZnIn 2 S 4. • The built-in electric field at the heterojunction interface can effectively promote carrier separation. [ABSTRACT FROM AUTHOR]

Enhancing the activity of the carbon dioxide reduction reaction (CO2RR) by controlling the structure of single-atom catalysts (SACs) has recently been shown to be a rather promising strategy. The effect of the structure and coordination environment on electrocatalytic CO2RR activity of single-atom copper catalysts (Cu–N/C) was investigated by using density functional theory (DFT) calculations. The free energies of the adsorption of intermediates *CO and *COOH are linearly correlated, and among 11 kinds of Cu–N/C catalysts, CuN3V and CuN2V2 have better CO2RR activity with ΔG*COOH as the descriptor. The free energy analysis of the CO2 electrocatalytic reduction reaction shows that CuN3V and CuN2V2 have the lowest limiting potentials in 11 Cu–N/C catalysts (−0.86 V and −0.93 V) too. For saturated structure catalysts, the production of *COOH is the decisive step, while the desorption of *CO is the decisive step for unsaturated ones. CuN3V and CuN2V2 have a high CO2RR selectivity, and their activation energy barriers for the CO2RR (1.37 eV and 1.32 eV) are much lower than that for the hydrogen precipitation reaction (HER, 3.22 eV and 4.53 eV). The change in the catalyst structure can affect not only the adsorption properties, but also the potential-determining step of the CO2RR, and the unsaturated structure is more favorable for improvement of the catalyst activity. These results highlight the important influence of the structure and coordination environment on the activity and selectivity of single-atom copper catalysts for the CO2RR, and provide helpful information for design of other metal single-atom catalysts. [ABSTRACT FROM AUTHOR]