Cu-Ag Tandem Catalysts for High-Rate CO2 Electrolysis toward Multicarbons

Tandem electrocatalysis decouples individual steps within a chemically complicated pathway via multicomponent catalyst design. Such a concept is attractive for CO2 electro-conversion to multicarbons (C2+), especially at high rates. Here, we show that a Cu-Ag tandem catalyst on a gas diffusion electrode (GDE) can enhance the C2+ production rate from CO2 through CO2 reduction to CO on Ag and subsequent carbon coupling on Cu. With added Ag, the C2+ partial current over a Cu surface increases from 37 to 160 mA/cm2 at −0.70 V versus reversible hydrogen electrode (RHE) in 1 M KOH with no mutual interference between the two metals. Moreover, the intrinsic C2H4 and C2H5OH activity in the tandem platform is significantly higher than Cu alone under either pure CO2 or CO atmosphere. Our results indicate that the CO-enriched local environment generated by Ag can enhance C2+ formation on Cu beyond CO2 or CO feeding, suggesting new mechanisms in a tandem three-phase environment.