Engineering of sulfur defects in ZnIn₂S₄ via pulsed laser ablation for enhanced photocatalytic CO₂ reduction performance

Vacancy defect engineering represents one of the most effective strategies for enhancing photocatalytic performance. However, the wide applications of vacancy defect engineering are confronted with the problems of lack of precise control over vacancy defect engineering and poor stability. Herein, we employed an advanced pulse laser ablation in liquid (PLAL) method to introduce sulfur vacancies on the ZnIn₂S₄ nanosheets. Specifically, the vacancy concentration on the ZnIn₂S₄ can be easily modulated by changing the time for PLAL. In addition, it is discovered that the introduction of sulfur vacancies on the ZnIn₂S₄ nanosheets can provide enormous surface-active sites and facilitate the photogenerated charge carrier, thereby enhancing the photocatalytic CO₂ conversion. Compared to the pristine ZnIn₂S₄, the sulfur vacancies-rich ZnIn₂S₄ nanosheets show 15-fold enhancement in photocatalytic CO₂ conversion performance towards CO production, reaching 365 µmol·g⁻¹·h⁻¹. In addition, the sulfur vacancy-rich ZnIn₂S₄ shows a high stability for photocatalytic CO₂ conversion, retaining its performance after 12 h of reaction. According to the mechanistic studies, it is revealed that the sulfur vacancies can also enhance the adsorption capability of ZnIn₂S₄, thereby reducing the potential barrier for subsequent conversion. This work demonstrates the potential of the PLAL strategy for not only precisely introducing vacancy defects on the semiconductors, but also enhancing the stability of the defects, which can pave new avenues for the photocatalytic applications.