Atomically Precise Gold Nanoclusters as Model Catalysts for Identifying Active Sites for Electroreduction of CO2

Abstract Accurate identification of active sites is critical for elucidating catalytic reaction mechanisms and developing highly efficient and selective electrocatalysts. Herein, we report the atomic‐level identification of active sites using atomically well‐defined gold nanoclusters (Au NCs) Au 25 , Au 38 , and Au 144 as model catalysts in the electrochemical CO 2 reduction reaction (CO 2 RR). The studied Au NCs exhibited remarkably high CO 2 RR activity, which increased with increasing NC size. Electrochemical and X‐ray photoelectron spectroscopy analyses revealed that the Au NCs were activated by removing one thiolate group from each staple motif at the beginning of CO 2 RR. In addition, density functional theory calculations revealed higher charge densities and upshifts of d ‐states for dethiolated Au sites. The structure–activity properties of the studied Au NCs confirmed that dethiolated Au sites were the active sites and that CO 2 RR activity was determined by the number of active sites on the cluster surface.