Defect-Mediated Cu–S Pair Active Sites Modulating Proton Supply to Facilitate Overall CO₂ Photoreduction with H₂O

Abstract

Precise design of photocatalysts with the demanded active surface structure for highly efficient and selective CO 2 photoreduction is crucial but challenging. Here, by taking CdS as a prototype, single-atom Cu is successfully constructed on Cd-deficient CdS (Cd 1– x S) to improve the performance of CO 2 photoreduction with H 2 O as proton donor. The optimal Cu/Cd 1– x S with Cd vacancies (V Cd )-mediated single-atom Cu exhibits nearly 100% selective CO production and a more than three-fold higher CO evolution rate compared to that of Cd 1– x S. Both experimental identification and DFT theoretical simulation unveil that the V Cd -mediated single-atom Cu render Cu–S pair sites to function as more catalytically active sites for dissociating H 2 O and promoting the corresponding proton supply, which favors the subsequent protonation of the adsorbed CO 2 at the adjacent Cd sites via the two-proton coupled two-electron transfer pathway. This work demonstrates the importance of modulating proton supply from the oxidation half-reaction for facilitating the overall CO 2 photoreduction, advocating an overall-reaction perspective for the design and development of highly efficient and selective CO 2 conversion photocatalysts.