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 (FE_CO, 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.