Surface-defect engineering of metal nanoclusters for highly efficient electrocatalytic CO 2 reduction

Abstract Defect engineering serves as a pivotal strategy for improving the performance of CO2 electrocatalytic reduction (CO2RR). However, understanding the structure-activity relationship between defect configurations and catalytic activity at the atomic level remains a significant challenge. This study utilized a series of structurally well-defined Au1Ag24+2n(SR)18+n (where n = 0, 1, 2; SR = adamantanethiol) nanoclusters as model catalysts to systematically explore the impact of defect engineering on CO2RR. In the Au1Ag26 nanocluster, rearrangement of the peripheral ligands creates structural defects, which increases the exposure of the active surface area. This defect engineering leads to optimal catalytic performance, achieving a Faradaic efficiency (FE) for CO of 63% at −1.0 V (vs. RHE)—nearly double that of Au1Ag24, which has an FE of 32%. In contrast, due to the surface units of Au1Ag28 being fully covered, its catalytic activity is negligible (FECO < 5%). By integrating comprehensive structural characterization with electrocatalytic performance analysis, we have demonstrated at the atomic level that the Ag1S3 motif acts as the possible catalytic active center, with catalytic performance exhibiting a direct correlation with the degree of active site exposure. This research uncovers the fundamental mechanism by which defect engineering enhances CO2RR catalyst performance by reconstructing the coordination environment and strategically exposing active sites of cluster-based catalysts.