Boosting Visible-Light Photocatalytic Syngas Production via Spatially Adjacent Dual Sites of Co Metal and Sulfur Vacancy in ZnIn <sub>2</sub> S <sub>4</sub>
Bin Liu, Xi Zhou, Hao Ma, Xianli Hu, Ruimei Fang, Wei Xu, Fan Dong
Abstract
Solar-driven conversion of CO 2 to syngas (CO/H 2 ) represents a promising approach for carbon-neutral fuel synthesis. However, achieving efficient and selective photocatalytic CO 2 reduction remains challenging due to competition from the hydrogen evolution reaction (HER) and inadequate spatial control over active site distribution. Herein, we introduce a Co-doped ZnIn 2 S 4 (CoZIS) photocatalyst, where Co doping induces the formation of adjacent Co metal sites and sulfur vacancies (Vs), establishing spatially coordinated dual active sites. This architecture enables selective CO 2 adsorption and activation at Co sites via d-p orbital hybridization coupled with proton reduction at neighboring Vs, thereby promoting proton-coupled electron transfer (PCET) and facilitating *COOH intermediate formation. The optimized CoZIS delivers a syngas production rate of 1314.8 μmol g – 1 h – 1 under visible-light irradiation, surpassing reported yields for many analogous sulfide-based photocatalysts. In-situ spectroscopic studies, kinetic isotope effect (KIE) experiments, and density functional theory (DFT) calculations demonstrate that the proximity of Co and Vs sites reduces the *COOH formation energy barrier while improving the charge separation efficiency. This work advances a versatile dopant-defect engineering strategy for creating synergistic dual sites that orchestrate CO 2 and proton reduction, offering broad implications for syngas production and carbon recycling technologies.