Electrochemical reduction of CO 2 at CuAu nanoparticles: size and alloy effects

Reduction of CO2 at Cu or Au electrodes typically yields methane or CO, respectively. Cu and Au nanoparticles and their alloys offer unique advantages over foil electrodes in terms of reduced overpotentials and product selectivities. In this work, we explore the electrochemical reduction of CO2 in aqueous electrolytes using alloys of Cu and Au including 2 and 6 nm nanoparticles along with polycrystalline foils. These results show the CuAu alloys primarily produce CO; however, yields are dramatically increased relative to Au. CuAu electrodes in the form of planar foils produce up to 3.4 times more CO yields relative to Au foil. Most remarkably, nanoparticle electrodes provide up to 12.5-fold CO yield increases relative to polycrystalline alloy foils and 175-fold CO yield increases relative to bulk Au foils. Voltammetry shows that onset potentials for CO2 reduction are shifted anodically with smaller nanoparticle sizes and with greater Au content. The dramatic increase in CO yields with nanoparticle alloys is attributed to the improved CO2 deoxygenation associated with Cu interfaces and the relatively facile desorption of CO from low-coordination Au sites.