Sulfur Vacancy-Engineered ZnIn2S4 Nanosheets Integrated with CoS1.097 for Enhanced Visible Light-Driven Nitrogen Photofixation

Herein, S-scheme heterojunction photocatalysts integrating sulfur vacancy-engineered ZnIn2S4 (Sv-ZnInS) with CoS1.097 (CoS) were successfully synthesized via a simple hydrothermal reaction. The formed CoS/Sv-ZnInS heterostructures exhibited considerably high catalytic activity toward visible light-driven photocatalytic nitrogen (N2) fixation. Notably, the optimized 3CoS/Sv-ZnInS sample achieved an ammonia yield of 18.18 ± 0.39 mg·L–1 after 1 h of visible-light illumination, which was an approximately 2.4-fold enhancement relative to pristine Sv-ZnInS. The S-scheme charge separation and transfer pathway was elucidated via in situ irradiated X-ray photoelectron spectroscopy, noble-metal loading, and band structure analysis. The underlying N2 photofixation mechanism was systematically investigated using density functional theory calculations and in situ diffuse reflectance infrared Fourier transform spectroscopy. The results revealed that N2 photofixation over the 3CoS/Sv-ZnInS catalyst occurred via a multistep proton-coupled electron transfer. Our findings indicate that S-scheme CoS/Sv-ZnInS heterojunctions may offer a viable route toward visible light-driven photocatalytic N2 fixation.