Site-specific synergy of CuNi dual atoms on hydroxyl-rich MXene for selective CO2 photoreduction

Photocatalytic CO 2 reduction in aqueous media represents a crucial route for solar-to-fuel conversion using water as the proton source. However, selectively driving multi-electron CO 2 reduction over the competing hydrogen evolution reaction (HER) remains challenging due to the complex proton-coupled electron transfer (PCET) reactions. Here, a hydrothermal approach is designed with in situ alkalization to anchor robust CuNi dual-atom sites on antioxidative hydroxyl-rich Ti 3 C 2 (OH) x MXene. The resulting Cu 1 Ni 1 /Ti 3 C 2 (OH) x catalyst achieves a high CO yield of 635.8 μmol·g −1 ·h −1 with 99.7 % selectivity and superior cycling stability, outperforming most reported MXene-based and diatomic-site catalysts. In situ spectroscopy and theoretical calculations reveal that Cu sites promote *COOH/*H formation and CO desorption, while Ni sites favor *COOH-to-*CO conversion and enhance water adsorption. This dual-atom synergy precisely regulates PCET at adjacent Cu and Ni sites, enabling HER suppression and enhanced CO generation. This work establishes a new paradigm for engineering stable MXene anchored dual-atom catalysts with site-specific functionalities for highly selective CO 2 photoreduction.