Author: Wenhao Ren (University of Adelaide) - Electrochemical CO2 reduction holds significant promises for carbon recycling and energy storage. The microenvironment at the interface structure can substantially influence the activity and selectivity of the reaction. However, the interface structure in a catholyte-free membrane electrode assembly (MEA) electrolyzer remains underexplored.
Here, we investigate CO2/CO reduction across different cell configurations, with a particular focus on the membrane electrode assembly (MEA) electrolyzer. Our analysis reveals the presence of a unique quasi two-phase interface in the MEA system, which fundamentally differs from the conventional three-phase interface typically observed in flow cells, including the proton accessibility, mass transport characteristics, and cation-related effects. To elucidate the nature and implications of this interface, we examine three critical aspects that govern the electrocatalytic reaction environment: (i) the effect of K+ at the electric double layer; (ii) the mass transfer of H2O from the anolyte to the cathode, providing protons; and (iii) the mass transfer of OH- from the cathode to the anode in the catholyte-free system.