Electrocatalytic CO2 reduction over Ag/CuSn Electrodes: Modulation of C1, C2, and C3+ products

Abstract

Combining different metals has proven to be an effective methodology for fabricating electrodes that can manipulate reduction products in electrochemical (EC) CO₂ reduction. In this study, CuSn and EC treated CuSn were surface-modified with Ag via sputter deposition. EC CO₂ reduction was performed at various applied potentials in KHCO₃, K₂CO₃, and KOH electrolytes. The effects of cations and anions were tested to examine the variation in reduction products. The major reduction products were H₂ and C₁ compounds (CO, CH₄, formate), as well as C₂ compounds (C₂H₄, ethanol, and acetate). Minor products included C₁ compounds (methanol), C₂ compounds (acetaldehyde and glycolaldehyde), and C₃₊ compounds (propanol and isopropanol), along with C₂H₆ and C₃₊ hydrocarbon products. The variation of C₂₊ hydrocarbons was explained by Fischer-Tropsch (F-T) chemistry. The oxidation states of Cu and Sn, as well as the Cu/Sn ratios, were examined before and after EC CO₂ reduction using depth-profiled X-ray photoelectron spectroscopy. The experimental factors—catalyst composition, applied potential, and electrolyte composition—interacted to create a complex reaction environment. This combined approach provides valuable insights into identifying optimal conditions for achieving desired product selectivity.