Atomic-Scale Interfacial Microenvironment Engineering of Au Nanoclusters via Electromagnetic Fields for Wide-pH CO ₂ Electroreduction

Precise surface engineering of gold nanoclusters (Au NCs) is critical for electrocatalysis, but conventional strategies frequently fail to maintain atomic precision, owing to rapid reaction kinetics and parasitic etching reactions. Herein, we develop an electromagnetic multifield coupling strategy to enable the reproducible synthesis of previously inaccessible Au25(SC18H37)18− nanoclusters, providing atomic-level insight into how ligand-induced surface microenvironments govern electrocatalytic CO2 reduction. Benchmarking their eCO2RR performance against the archetypal Au25(PET)18− reveals a clear activity trend of Au25(SC18H37)18− < Au25(SC12H25)18− < Au25(PET)18− < Au25(SC6H13)18−. In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy demonstrates that ligand hydrophobicity, in concert with electrolyte anions, restructures interfacial water to suppress the competing HER while promoting *COOH formation, thereby dictating CO2 to CO selectivity. Density functional theory and ab initio molecular dynamics simulations reveal that ligand-dependent stabilization of the *COOH intermediate governs the rate-determining step, with Au25(SC6H13)18− exhibiting optimal energetics that accelerate CO formation and desorption. Explicit solvation models show that more polarizable Br− and I− anions further stabilize *COOH and lower reaction barriers relative to Cl−. These findings identify ligand microenvironments and electrolyte anions as key regulators of eCO2RR kinetics.