Electrochemical CO₂ reduction to CO on dendritic Ag-Cu electrocatalysts prepared by electrodeposition

Ag, Ag-Cu and Cu dendrite catalysts were electrochemically prepared on a Cu foil substrate to investigate their catalytic activity and selectivity for electrochemical CO₂ reduction to CO. As the Cu content increased, the morphologies of Ag-Cu dendrite catalysts changed significantly from round to flower-like shapes accompanied by a decrease in branch size of the dendritic structure. A crystallographic study of the Ag-Cu dendrite catalysts demonstrated the formation of Ag and Cu co-deposits, while a compositional characterization confirmed the presence of a Cu-rich surface. Among the synthesized dendrite catalysts, the Ag₁₀₀ dendrite catalyst achieved the highest CO faradaic efficiency of 64.6% at a constant potential of -1.7 V_SCE in CO₂-saturated 0.5 M KHCO₃ electrolyte. However, the catalytic activity of Ag₅₇Cu₄₃ dendrite catalyst was 2.2 times higher than that of the Ag₁₀₀ dendrite catalyst, in terms of Ag mass activity. By controlling the composition of Ag and Cu, direct formation of syn-gas or enhancement in the mass activity to CO production was achievable.