Is Hydroxide Just Hydroxide? Unidentical CO₂ Hydration Conditions during Hydrogen Evolution and Carbon Dioxide Reduction in Zero-Gap Gas Diffusion Electrode Reactors

The implementation of gas diffusion electrodes is a prerequisite to achieving industrially relevant reaction rates in gas-phase electrochemical CO2 reduction (CO2RR). In the state-of-the-art anion exchange membrane flow electrolyzers, however, there substantial loss reactants due nonelectrochemical consumption at cathode and transport its products anode. Our detailed analysis crossover zero-gap CO2-to-CO electrolyzer showed change chemical nature transported ionic species through membrane. With increasing rate, continuous shift from HCO3– CO32– conduction was found be similar pure carbonate high current density region (>100 mA cm–2). As competing hydrogen evolution takes over cathodic CO2-rich environment, hydroxide becomes more pronounced. This reveals an alteration consumption, so-called hydration (CO2 + OH– ↔ CO32–), implying unidentical environment for ions generated CO2RR under atmosphere. work draws attention incomplete description confined cathode/membrane interface electrode assembly-type electrolyzers.