Ultrathin 2D In 2 O 3 Nanosheets Confining Cu Single Atoms Synergized With Oxygen Vacancies for High Selectivity of Photocatalytic Reduction of CO 2 to CO

ABSTRACT In this work, we constructed an ultrathin two‐dimensional (2D) In 2 O 3 nanosheet (In 2 O 3 ‐Ns) structure based on oxygen vacancies (O V )‐rich defects and low crystallinity to anchor Cu single atoms (Cu SAs) and synthesized Cu/In 2 O 3 ‐Ns photocatalysts. Benefiting from the synergistic strategy of Cu single atoms and In 3+ ‐O V , CO 2 molecules were activated, the energy barrier for the formation of the * COOH intermediates was lowered, and the CO yield is increased to 17.24 µmol g −1 h −1 with near‐unity selectivity (>99%). Moreover, Cu/In 2 O 3 ‐Ns photocatalysts demonstrate exceptional stability over extended cycling tests (64 h). In situ spectral characterization and DFT calculations reveal that the engineered two‐dimensional ultrathin In 2 O 3 ‐Ns structures demonstrate significant advantages in promoting CO 2 enrichment and confining key reaction intermediates following the anchoring of Cu single atoms, thereby substantially enhancing the surface coverage of * COOH species. Cu single atoms and In 3+ ‐O V sites synergistically promote * CO 2 adsorption, * COOH formation/desorption, and accelerate the transfer of photoexcited charge carriers between In 2 O 3 matrix and Cu single atoms. This cooperative mechanism significantly enhances both the photocatalytic CO 2 reduction activity and CO selectivity. This work provides a novel strategy for constructing precisely tailored active sites in photocatalysts and offers fundamental insights into boosting the efficiency and selectivity of photocatalytic CO 2 conversion.