Basal Plane Activation of SnS 2 Thin‐Film by Fluorine Doping for Selective Solar‐Driven CO 2 Reduction With Enhanced Quantum Efficiency

Photocatalytic conversion of CO₂ into value-added fuels offers a viable approach to combat climate change and address global energy demands. Here, we present a fluorine-doped SnS₂ thin film with sulfur vacancy (i.e., S_V-SnS₂:F), prepared via thermal evaporation, post-sulfurization, and fluorine ion-implantation. Substitution of sulfur with fluorine and sulfur vacancy formation changes the product selectivity from CH₄ to CO with about 40-fold enhanced yield and boosted internal quantum efficiency (IQE) of 0.52%. Transient absorption, in situ near-ambient pressure X-ray photoelectron, and in situ Fourier transform infrared spectroscopies, along with first-principles density functional theory calculations, suggest that nearest-neighbor Sn to F serves as an active site and stabilizes the *COOH intermediate. Our findings shed light on how F doping activates the nearby elements and its crucial role in intermediate stabilization toward selectivity change in a heterogeneous photocatalysis process.