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

Abstract

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.