Structural Isomerization of Au₂₈ Nanoclusters Induces Catalytic Difference in CO₂ Electroreduction

Atomically precise gold nanoclusters (Au NCs) have emerged as a unique class of CO₂ reduction reaction (CO₂RR) electrocatalysts, because of their well-defined active sites and tunable electronic structures. However, the influence of structural isomerism on their electrocatalytic performance has been scarcely explored. Herein, we combined theoretical simulations and experiments to systematically investigate the electrocatalytic difference of two Au₂₈(CHT)₂₀ (CHT = cyclohexanethiolate) isomers with the same core but distinct spatial configurations (Au_28i and Au_28ii) in the CO₂RR process. The simulation results reveal that the Au_28i isomer facilitates more facile desorption of thiolate ligands and the exposed Au sites exhibit better electrocatalytic CO₂RR activity to promote CO formation. The higher activity in Au_28i results from its higher position of the d-band center in the active Au sites and the less-ordered water structure at the electrochemical interface, leading to enhanced adsorption of reaction intermediates and lowering the kinetic barrier for the proton transfer process. In great agreement with theoretical predictions, we experimentally demonstrate that Au_28i exhibits remarkable CO₂RR performance, delivering a CO faradaic efficiency (FE_CO) of approximately 90% and a higher CO partial current density, as well as enhanced stability relative to that of Au_28ii. This study elucidates the isomerization-induced catalytic distinction in metal nanoclusters, providing crucial guidance for the rational design of highly efficient nanocatalysts through precise structural engineering.