Synchronizing directional photogenerated electrons and holes through Ag and Bi bimetallic modification toward sustained hydrogenation process in CO2 methanation reaction

Sustained photocatalytic hydrogenation of CO₂ molecules is crucial for the CO₂ methanation reaction. Synchronizing directional photogenerated charge carriers and regulating the activation and hydrogenation process of CO₂ molecules are key to achieving the efficient photocatalytic methanation of CO₂. Herein, Ag–Bi bimetallic sites were designed and anchored on the surface of TiO₂ via a one-step solution impregnation reduction and applied for the photocatalytic conversion of CO₂ to CH₄. The optimum 5 %Ag₉₀Bi₁₀-TiO₂ composite exhibited excellent photocatalytic performance for the photoreduction of CO₂ into CH₄. The product selectivity of CH₄ reached up to 97.2 %, at a rate of 58.9 μmol·g⁻¹·h⁻¹. In situ Kelvin probe force microscopy and diffuse reflectance infrared Fourier transform spectroscopy attributed the high selectivity of CH₄ to the coexistence of metallic Ag and Bi sites, which induced directional photogenerated electrons and hole transfer. Moreover, the synergistic function of Ag–Bi bimetallic active sites on TiO₂ facilitated the hydrogenation of *CO₂^– to CH₄. The proposed strategy provides insight into the design of highly selective photocatalysts for the reaction of photocatalytic methanation of CO₂.