Spatially Coupled Pd _SA -Ovs Dual Sites on TiO ₂ for Synergistic Regulation of CO ₂ Photoreduction to CH ₄

Efficient photocatalytic reduction of carbon dioxide (CO 2 ) to methane (CH 4 ) relies on a continuous proton-coupled electron transfer process, which places high demands on the spatial arrangement and functional synergy of catalytic active sites. Herein, we propose a vacancy-directed oxygen-bridge scission and coordination coupling (VD-OSCC) strategy, successfully establishing spatially coupled (adjacent and functionally complementary) dual-active sites composed of palladium single atoms and oxygen vacancies (Pd SA -Ovs) on the surface of TiO 2 . These dual sites collaboratively regulate directional charge transfer and ensure efficient proton transport, thereby creating a favorable microenvironment for the multi-step proton-electron coupling process. Ovs sites primarily facilitate the adsorption and activation of CO 2, while the adjacent Pd SA sites act as efficient hole-trapping centers for accelerating water dissociation to continuously supply protons in CO 2 hydrogenation. Furthermore, the adjacent configuration of Pd SA and Ovs provides protons with the shortest migration path, effectively facilitating the proton-coupled electron transfer process. The designed Pd SA -Ovs exhibit selectivity of 91.8% for CO 2 reduction to CH 4 with a corresponding production rate of 46.57 μmol g −1 h −1 in pure water. This work provides insights into the design of synergistic neighboring adjacent active sites photocatalysts to achieve highly efficient and selective photocatalytic reduction of CO 2 to CH 4 .