Confinement of Atomically Dispersed Ru Sites via Metal Defects Over Ultrathin Layered Double Hydroxide for Efficient Photocatalytic CO ₂ Reduction

Single‐atom catalysts (SACs) are regarded as promising photocatalysts due to their maximized atomic utilization efficiency. However, achieving stable and efficient SACs remains challenging owing to the strong aggregation tendency of metal atoms. In this study, CoAl‐layered double hydroxide (LDH) is used as a support, with metal vacancies introduced on its surface by controlling the material thickness. Ru atoms are anchored at these vacancy sites, achieving atomic‐level dispersion and effectively preventing aggregation into clusters. The Ru single atom formed an unsaturated coordination environment with the LDH support, where the unsaturated coordination around Ru markedly enhanced CO 2 adsorption and activation. Meanwhile, these well‐dispersed active centers generate a high density of catalytically active sites, which effectively modulate the spatial distribution of photogenerated charges across the catalyst surface. The results demonstrate that the ultrathin LDH loaded with 1.0 wt% Ru photocatalyst achieves a CO production rate of 4663.34 µmol g −1 h −1 , nearly doubling the performance of bulk LDH loaded with 1.0wt% Ru. Density functional theory (DFT) calculations further confirm that u‐1.0wt%Ru‐LDH effectively stabilizes the COOH * intermediate, reducing the energy barrier for protonation and accelerating the CO 2 reduction reaction. This study offers insights into single‐atom photocatalyst design and underscores the potential of single‐atom engineering for photocatalysis.