ReS₂ Nanosheets with In Situ Formed Sulfur Vacancies for Efficient and Highly Selective Photocatalytic CO₂ Reduction

Artificial photosynthesis can provide valuable fuels and positively impact greenhouse effects, via transforming carbon dioxide (CO₂) and water (H₂O) into hydrocarbons using semiconductor-based photocatalysts. However, the inefficient charge-carrier dissociation and transportation as well as the lack of surface active sites are two major drawbacks to boosting their activity and selectivity in photocatalytic CO₂ reduction. Recently, ReS₂ has received tremendous attention in the photocatalysis area due to its intriguing physicochemical properties. Nevertheless, the application of ReS₂ in photocatalytic CO₂ reduction is scarcely covered. Herein, a heterojunction formed between ReS₂ nanosheets and CdS nanoparticles is reported, achieving an apparently raised CO production of 7.1 μmol g^-1 and high selectivity of 93.4%. The as-prepared ReS₂/CdS heterojunction exhibits strengthened visible-light absorption, high-efficiency electron-hole pair separation/transfer, and increased adsorption/activation/reduction of CO₂ on in situ created sulfur vacancies of ReS₂, thus all favoring CO₂ photoreduction. These are corroborated by advanced characterization techniques, e.g., synchrotron-based X-ray absorption near-edge structure, and density functional theory-based computations. The findings will be of broad interest in practical design and fabrication of surface active sites and semiconductor heterojunctions for applications in catalysis, electronics, and optoelectronics.