Hydroxyl‐Mediated Proton Transfer Over Cu Single Atoms Decorated TiO 2 for Selective Photocatalytic CO 2 Reduction to Ethanol

Photocatalytic CO 2 reduction to hydrocarbon fuels represents a sustainable route toward carbon neutrality, yet selective and efficient C 2 production remains a formidable challenging due to the high thermodynamic barrier and sluggish C–C coupling kinetics. In this study, we report a hydroxyl (–OH)‐rich TiO 2 photocatalyst decorated with Cu single atoms (SAs) (Cu/HTO) that addresses this challenge through synergistic active site—surface group engineering. The electronic interplay between surface –OH groups and Cu SAs promotes charge separation and strengthens CO 2 chemisorption/activation at Cu sites, facilitating *CO intermediates formation and subsequent protonation for selective C 2 H 5 OH and CO prodution. Under sacrificial agent free conditions, Cu/HTO delivers CO at 90.1 µmol g −1 h −1 with 88.3% yield‐based selectivity in a gas–solid (GS) system. Notably, in a gas–liquid–solid (GLS) system with water supplying abundant protons, Cu/HTO efficiently yields C 2 H 5 OH at 361.5 µmol g −1 h −1 with 99.4% yield‐based selectivity, which is related to Cu 2+ sites stabilized *CO intermediates thermodynamically favoring C–C coupling and the surface –OH groups mediated proton transfer kinetically facilitating multistep protonation. This work not only establishes a high‐performance and low‐cost photocatalyst for CO 2 ‐to‐C 2 conversion but also provides a rational design paradigm for engineering single‐atom–surface‐group synergy in solar fuel synthesis.