Dopant Engineering of Isostructural Metal Nanoclusters for Modulating CO2 Electroreduction.

Achieving atomic-level insight into how dopants regulate the electrocatalytic CO2 reduction reaction (eCO2RR) of metal nanoparticles is challenging due to the lack of well-defined, compositionally tunable, and structurally identical model systems. Herein, we report two isostructural nanoclusters: [Au10Ag4(DPPP)5Cl4]2+ (Au10Ag4) and [Au9Ag2Cu3(DPPP)5Cl4]2+ (Au9Ag2Cu3), which differ only in metal composition (Au─Ag vs. Au─Ag─Cu). Together with the isostructural monometallic [Au14(DPPP)5Br4]2+ (Au14), they serve as ideal platforms to elucidate dopant effects on eCO2RR. Electrochemical studies reveal that Ag doping (Au10Ag4) suppresses both CO selectivity and activity of Au14, whereas further Cu incorporation (Au9Ag2Cu3) not only enhances these metrics relative to Au10Ag4 but also surpasses Au14. Specifically, Au9Ag2Cu3 exhibits an enhanced CO Faradaic efficiency (FECO, 73.7%-95.5%), exceeding that of Au14 (63.6%-95.0%) and Au10Ag4 (66.2%-79.5%), and its CO partial current densities were improved by 1.5- and 2.6-fold compared to those of Au14 and Au10Ag4, respectively. Theoretical calculations and in situ experiments reveal that Ag─Cu co-doping lowers the energy barrier for *COOH formation and weakens CO binding, promoting CO2-to-CO conversion. In contrast, Ag doping alone raises the energy barrier for *COOH formation and impedes CO desorption, diminishing catalytic activity. These findings provide atomistic insights into dopant-regulated eCO2RR and inspire the rational design of advanced alloy electrocatalysts.