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 VSCE 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.