Closing the electron/proton kinetic disconnect via interfacial proton spillover on adjacent Ag-Bi bimetallic surface enables efficient photocatalytic CO2 methanation

A dual-scale Ag-Bi/TiO 2 -Ov architecture couples photogenerated electrons with interfacial protons, resolving the kinetic disconnect in CO 2 methanation. • Adjacent Ag-Bi sites synergistically lower the barrier for *COOH formation while facilitating proton spillover from TiO 2 -Ov. • The optimized photocatalyst achieves a CH₄ evolution rate of 75.17μmol·g −1 ·h −1 with 97.2% selectivity under sacrificial-agent-free conditions. Solar-driven CO 2 -to-CH 4 conversion could help close the anthropogenic carbon loop, yet its practical realization is consistently undermined by poor selectivity and a kinetic disconnect between interfacial electron transfer and proton availability. Herein, we address these limitations by constructing a dual-scale architecture that deliberately couples proton spillover dynamics with CO 2 activation pathways. Highly dispersed Ag-Bi hetero-bimetallic nanoalloys are integrated onto oxygen-vacancy-enriched TiO 2 through a one-step reductive transformation of metal oxyacid precursors, establishing atomically intimate Ag-Bi dual active sites. Operando diffuse reflectance infrared Fourier transform spectroscopy coupled with density functional theory calculations reveals that this bimetallic interface not only lowers the *CO 2 →*COOH free-energy barrier and stabilizes *CO intermediates to suppress parasitic desorption, but also orchestrates directional proton spillover via localized electrostatic modulation. Electrons relayed from the oxygen-vacancy-rich TiO 2 converge spatially with protons generated in situ at surface oxygen vacancies, establishing a concerted proton-coupled electron transfer channel that governs the sequential hydrogenation of adsorbed *CO to CH 4 . Guided by this mechanistic rationale, the optimized photocatalyst (A 1 B 1 T30) achieves a CH 4 production rate of 75.17 μmol·g −1 ·h −1 with 97.2% selectivity. By resolving how electrons and protons converge at the interface, the work identifies a concrete materials lever for selective C 1 photoreduction. Download: Download high-res image (196KB) Download: Download full-size image