Ionomers impact the performance of gas diffusion electrodes for electrochemical CO2 reduction

Ionomers modulate the microenvironment in gas diffusion electrodes (GDEs) for electrochemical CO 2 reduction and can play a decisive role in the development of active and stable electrodes required for industrial implementation. This is achieved by different mechanisms influencing the adsorption and transport parameters, local values of pH and reactant concentrations as well as the wettability of the pore system. We analyze the existing literature describing the impact of ionomers on GDEs for CO 2 reduction on silver catalysts, yielding carbon monoxide, and on copper catalysts promoting the formation of C 2+ products. Despite remarkable progress in recent years, it is still challenging to attribute the changes in the electrode performance to the distinct roles of ionomers due to the multitude of processes occurring and the complexity of the electrodes. We propose to complement advanced experimental techniques for operando studies of working electrodes with simulations obtained from model systems with simplified architectures. • Ionomers impact the performance of gas diffusion electrodes for CO 2 reduction. • Ag catalysts for CO production and Cu catalysts for C-C coupling. • Distinct roles of ionomers on electrode performance yet to be determined. • Research linking advanced operando techniques with model system studies required.