Ruthenium Single Atomic Sites Surrounding the Support Pit with Exceptional Photocatalytic Activity

Abstract Single‐metal atomic sites and vacancies can accelerate the transfer of photogenerated electrons and enhance photocatalytic performance in photocatalysis. In this study, a series of nickel hydroxide nanoboards (Ni(OH) x NBs) with different loadings of single‐atomic Ru sites ( w ‐SA‐Ru/Ni(OH) x ) were synthesized via a photoreduction strategy. In such catalysts, single‐atomic Ru sites are anchored to the vacancies surrounding the pits. Notably, the SA‐Ru/Ni(OH) x with 0.60 wt % Ru loading (0.60‐SA‐Ru/Ni(OH) x ) exhibits the highest catalytic performance (27.6 mmol g −1 h −1 ) during the photocatalytic reduction of CO 2 (CO 2 RR). Either superfluous (0.64 wt %, 18.9 mmol g −1 h −1 ; 3.35 wt %, 9.4 mmol −1 h −1 ) or scarce (0.06 wt %, 15.8 mmol g −1 h −1 ; 0.29 wt %, 21.95 mmol g −1 h −1 ; 0.58 wt %, 23.4 mmol g −1 h −1 ) of Ru sites have negative effect on its catalytic properties. Density functional theory (DFT) calculations combined with experimental results revealed that CO 2 can be adsorbed in the pits; single‐atomic Ru sites can help with the conversion of as‐adsorbed CO 2 and lower the energy of *COOH formation accelerating the reaction; the excessive single‐atomic Ru sites occupy vacancies that retard the completion of CO 2 RR.