Boosting Solar‐Driven CO₂ Conversion to Ethanol via Single‐Atom Catalyst with Defected Low‐Coordination Cu‐N₂ Motif

Abstract

Abstract Cu‐based catalysts have been shown to selectively catalyze CO 2 photoreduction to C 2+ solar fuels. However, they still suffer from poor activity and low selectivity. Herein, we report a high‐performance carbon nitride supported Cu single‐atom catalyst featuring defected low‐coordination Cu‐N 2 motif (Cu‐N 2 ‐V). Lead many recently reported photocatalysts and its Cu‐N 3 and Cu‐N 4 counterparts, Cu‐N 2 ‐V exhibits superior photocatalytic activity for CO 2 reduction to ethanol and delivers 69.8 μmol g −1 h −1 ethanol production rate, 97.8 % electron‐based ethanol selectivity, and a yield of ~10 times higher than Cu‐N 3 and Cu‐N 4 . Revealed by the extensive experimental investigation combined with DFT calculations, the superior photoactivity of Cu‐N 2 ‐V stems from its defected Cu‐N 2 configuration, in which the Cu sites are electron enriched and enhance electron delocalization. Importantly, Cu in Cu‐N 2 ‐V exist in both Cu + and Cu 2+ valence states, although predominantly as Cu + . The Cu + sites support the CO 2 activation, while the co‐existence of Cu + /Cu 2+ sites are highly conducive for strong *CO adsorption and subsequent *CO‐*CO dimerization enabling C−C coupling. Furthermore, the hollow microstructure of the catalyst also promotes light adsorption and charge separation efficiency. Collectively, these make Cu‐N 2 ‐V an effective and high‐performance catalyst for the solar‐driven CO 2 conversion to ethanol. This study also elucidates the C‐C coupling reaction path via *CO‐*CO to *COCOH and rate‐determining step, and reveals the valence state change of partial Cu species from Cu + to Cu 2+ in Cu‐N 2 ‐V during CO 2 photoreduction reaction.