High productivity of C2 hydrocarbons by stepwise C-C coupling and hydrogenation on multisite photocatalyst

High production capacity of C 2 products from CO 2 photoreduction remains a significant challenge owing to the difficulty of C-C coupling and weak hydrogenation. Herein, a novel stepwise C-C coupling and hydrogenation mechanism is developed on multisite catalyst to enhance the performance of photocatalytic CO 2 reduction to C 2 products. The active Co cluster, carbon dots (CDs) and Cs 3 Bi 2 Br 9 quantum dots (QDs) are reinforced with robust carbon matrix, which allows to accelerate mass/electron transport and improve stability of catalytic sites, enabling a competitive C 2 H 4 evolution rate of 57.60 μmol g cat −1 h −1 with 67.70 % C 2 H 4 selectivity. In situ experiments coupled with theoretical calculations verify that Co and CDs capture photogenerated electrons from Cs 3 Bi 2 Br 9 to form key intermediate Co-*CO-*CO-CDs. After *CO-*CO coupling on Co site, the proximal CDs provide plenty of protons to conduct continuous hydrogenation toward coupling site until C 2 H 4 is formed. This study paves a novel pathway to regulate C-C coupling and hydrogenation for CO 2 conversion to C 2 hydrocarbons.