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.