One‐Step Molten Salt Inducing Copper(I) and Sulfur Vacancies Decoration in In ₂ S ₃ Nanocrystals to Regulate Photocatalytic CO ₂ Reduction to Syngas

ABSTRACT To address key challenges in photocatalytic CO 2 reduction for syngas production—including low catalyst activity, difficult product ratio control, and poor photogenerated charge separation efficiency, a one‐step molten salt strategy was utilized to synthesize Cu + ‐doped In 2 S 3 , which achieves photocatalytic CO 2 reduction to syngas with yields of CO:H 2 ≈ 1:1. The introduced Cu + ions create sulfur vacancies, synergistically boosting CO 2 adsorption, charge separation, and light‐harvesting. Importantly, density functional theory (DFT) calculations confirm that Cu + doping effectively reduces the formation energy barrier of the key * CO intermediate, providing a thermodynamic driving force for the selective reduction of CO 2 to CO. This effectively promotes CO 2 adsorption and activation while thermodynamically lowering the energy barrier for the CO 2 reduction reaction. This study elucidates the synergistic enhancement mechanism between Cu + and sulfur vacancies and provides a feasible strategy for developing solar‐driven photocatalysts for CO 2 reduction.