Fig. 5. Performance of catalysts for electrochemical CO₂ reduction reaction.

Potential-dependent faradaic efficiency of the products from the CO₂RR products on electropolished Cu (a), chlorinated Cu (b), brominated Cu (c), and iodinated Cu (d). Anodic halogenation of Cu was performed in 0.1 M KCl at 1.1 V vs. Ag/AgCl for 100 s (b); in 0.1 M KBr at 0.18 V vs. Ag/AgCl for 60 s (c); in 0.1 M KI at −0.2 V vs. Ag/AgCl for 1 s (d). e–h FEs of C₁, C₂, and C₃ products from the same results shown in the corresponding upper plot. C₁ products include CO, formate, and CH₄. C₂ products include C₂H₄, ethanol, acetate, acetaldehyde, and glycolaldehyde. C₃ products include n-propanol, propionaldehyde, and allyl alcohol. Data were acquired during 40 min of electrochemical CO₂RR at a constant potential in 0.1 M KHCO₃ saturated with CO₂. FE is shown as a function of the iR-corrected potential in RHE scale. Data legends apply to all plots in the same row. Source data are provided as a Source data file.