Organic Additive-derived Films on Cu Electrodes Promote Electrochemical CO₂ Reduction to C₂₊ Products Under Strongly Acidic Conditions
Electrochemical CO₂ reduction (CO₂R) at low pH is desired for high CO₂ utilization; the competing hydrogen evolution reaction (HER) remains a challenge. High alkali cation concentration at a high operating current density has recently been used to promote electrochemical CO₂R at low pH. Herein we report an alternative approach to selective CO₂R (>70 % Faradaic efficiency for C₂₊ products, FE_(C2+)) at low pH (pH 2; H₃PO₄/KH₂PO₄) and low potassium concentration ([K⁺]=0.1 M) using organic film-modified polycrystalline copper (Modified-Cu). Such an electrode effectively mitigates HER due to attenuated proton transport. Modified-Cu still achieves high FE_(C2+) (45 % with Cu foil /55 % with Cu GDE) under 1.0 M H₃PO₄ (pH≈1) at low [K⁺] (0.1 M), even at low operating current, conditions where HER can otherwise dominate.
© 2023 Wiley-VCH. This material is based on work performed by the Liquid Sunlight Alliance, which is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under Award Number DE-SC0021266. The Resnick Sustainability Institute at Caltech is also acknowledged for its support of enabling infrastructure and facilities. We thank Dr. Yueshen Wu for SEM measurement assistance. We thank Dr. Shaoyang Lin for GC-MS measurement assistance. Data Availability Statement. The data that support the findings of this study are available in the Supporting Information of this article. The authors declare no conflict of interest.