Understanding the role of Zn vacancy induced by sulfhydryl coordination for photocatalytic CO2 reduction on ZnIn2S4

How to regulate the energy barrier of *COOH is the rate determining step of the photocatalytic reduction of CO2 to produce gaseous CO. Herein, an appropriate Zn vacancy on ZnIn2S4 was synthesised to achieve the desired photocatalytic CO2 reduction capacity (CO: 5.63 mmol g−1 h−1) and selectivity (CO: 97.9%). Various sulfhydryl groups were selected to regulate the Zn vacancy formation in ZnIn2S4, which directly generated the unsaturated coordination state of the sulfur adjacent to the Zn vacancy accompanied by less electrons when compared to ZnIn2S4 without Zn vacancy. Comprehensive experimental analysis and theoretical calculations demonstrated that the appropriate Zn vacancy tuned the Gibbs free energy of *COOH from the endothermic process to the exothermic process in the process of the photoreduction CO2. This work provided an engineering method for cation vacancies and improvement of the efficiency of photocatalytic CO2 reduction by adjusting the energy barrier of intermediate.