Authors: Sven Brückner, Wen Ju, Peter Strasser
Published: 2025-02-11
Source: Full article
AbstractThe acid‐base reaction of CO2 with hydroxide ions to (bi)carbonate anions at the cathode of alkaline exchange membrane (AEM) CO2 electrolyzer has detrimental impact on their performance. (Bi)carbonate buffers the local cathode pH, and in combination with metal cations, may lead to precipitation of salts at the cathode. This non‐electrochemical conversion of CO2 significantly reduces the CO2 utilization efficiency and limits the CO2 single pass conversion of AEM CO2 electrolyzer to 50% if CO is desired. Acidic metal cation‐free CO2 electrolysis has the potential to address and mitigate these problems. Here, CO2 valorization is demonstrated at faradaic CO efficiencies (FE) of up to 80% FECO in forward‐bias BPM cell architectures using actual neutral pure water feeding at the anode. This study demonstrates how immobilized anion exchange ionomer layers thereby facilitate the metal cation‐free CO2 valorization thanks to their positively charged functional NR4 groups. Unlike metal cations, the immobilized positively charged groups are not washed out of the reactor. This study shows that careful design of the distribution and location of the anion exchange ionomer molecules within the Gas Diffusion Electrode is key to efficient CO2‐to‐CO electrolyzer cell.