The role of ionomers in the electrolyte management of zero-gap MEA-based CO2 electrolysers: A Fumion vs. Nafion comparison

We study the role of binders (ionomers) in determining the life-span of gas diffusion electrodes (GDEs) used for high throughput CO2-to-CO electrolysis. We compare two typical ionomer materials (Nafion and Fumion, both are widely used for the preparation of Ag nanoparticles-based catalyst inks) to show that when used in zero-gap membrane/electrode assemblies, Fumion-containing inks are superior to Nafion-based ones and can uphold a very high CO-selectivity in the electrochemical CO2 reduction reaction for longer time. This is due to the ability of Fumion containing inks to suppress precipitation inside the GDE structure. As Fumion-fixed GDEs are significantly less hydrophobic than Nafion-fixed ones, our results contradict the widely accepted opinion that it is their non-wettability what mostly protects CO2-reducing GDEs from flooding. In turn, we argue that it is more important to maintain efficient electrolyte drainage pathways in the GDE structure, and explain the superiority of Fumion-fixed GDEs on this basis.