Boosting CO2 Electrochemical Reduction with Atomically Precise Surface Modification on Gold Nanoclusters

Abstract Thiolate‐protected gold nanoclusters (NCs) are promising catalytic materials for the electrochemical CO 2 reduction reaction (CO 2 RR). In this work an atomic level modification of a Au 23 NC is made by substituting two surface Au atoms with two Cd atoms, and it enhances the CO 2 RR selectivity to 90–95 % at the applied potential between −0.5 to −0.9 V, which is doubled compared to that of the undoped Au 23 . Additionally, the Cd‐doped Au 19 Cd 2 exhibits the highest CO 2 RR activity (2200 mA mg −1 at −1.0 V vs. RHE) among the reported NCs. This synergetic effect between Au and Cd is remarkable. Density‐functional theory calculations reveal that the exposure of a sulfur active site upon partial ligand removal provides an energetically feasible CO 2 RR pathway. The thermodynamic energy barrier for CO formation is 0.74 eV lower on Au 19 Cd 2 than on Au 23 . These results reveal that Cd doping can boost the CO 2 RR performance of Au NCs by modifying the surface geometry and electronic structure, which further changes the intermediate binding energy. This work offers insights into the surface doping mechanism of the CO 2 RR and bimetallic synergism.