This study presents a novel trimetallic single-atom alloy catalyst, Cu92Sb5Pd3, which efficiently and stably converts CO2 into CO, surpassing noble metal catalysts. The catalyst, composed of copper with isolated antimony and palladium atoms, achieves a high CO selectivity of 100% at -402 mA cm−2 and a high activity up to -1 A cm−2 in a neutral electrolyte. It exhibits long-term stability over 528 hours at -100 mA cm−2 with an FE_CO above 95%. Operando spectroscopy and theoretical simulations show that Sb and Pd single atoms synergistically shift the electronic structure of Cu to favor CO production and suppress hydrogen evolution. The collaborative interactions enhance the catalyst's stability. The results demonstrate that Sb/Pd-doped Cu can efficiently perform CO2 electrolysis under mild conditions, challenging the dominance of noble metals in large-scale CO2-to-CO conversion. The study highlights the importance of designing catalysts that balance selectivity and activity for efficient CO2 conversion. The trimetallic alloy shows superior performance in terms of current density, selectivity, and durability compared to noble metal catalysts. The catalyst's performance is attributed to the synergistic effects of Sb and Pd single atoms, which modulate the electronic structure of Cu to favor CO production and inhibit HER. The study provides insights into the design of efficient and stable CO2 conversion catalysts.This study presents a novel trimetallic single-atom alloy catalyst, Cu92Sb5Pd3, which efficiently and stably converts CO2 into CO, surpassing noble metal catalysts. The catalyst, composed of copper with isolated antimony and palladium atoms, achieves a high CO selectivity of 100% at -402 mA cm−2 and a high activity up to -1 A cm−2 in a neutral electrolyte. It exhibits long-term stability over 528 hours at -100 mA cm−2 with an FE_CO above 95%. Operando spectroscopy and theoretical simulations show that Sb and Pd single atoms synergistically shift the electronic structure of Cu to favor CO production and suppress hydrogen evolution. The collaborative interactions enhance the catalyst's stability. The results demonstrate that Sb/Pd-doped Cu can efficiently perform CO2 electrolysis under mild conditions, challenging the dominance of noble metals in large-scale CO2-to-CO conversion. The study highlights the importance of designing catalysts that balance selectivity and activity for efficient CO2 conversion. The trimetallic alloy shows superior performance in terms of current density, selectivity, and durability compared to noble metal catalysts. The catalyst's performance is attributed to the synergistic effects of Sb and Pd single atoms, which modulate the electronic structure of Cu to favor CO production and inhibit HER. The study provides insights into the design of efficient and stable CO2 conversion catalysts.