How Catalyst Dispersion Solvents Affect CO2 Electrolyzer Gas Diffusion Electrodes

Cathode gas diffusion electrodes (GDEs) in CO2 electrolyzers facilitate reagent transport and the reduction of CO2 into chemicals and fuels. While GDEs are routinely leveraged to achieve high rates of product formation, design principles for high-performing cathodes have not yet been established. In this report, we demonstrate the influence of a central parameter in GDE fabrication, the catalyst ink solvent, on the properties and performance of spray-coated cathode GDEs. We show that the choice of solvent used during catalyst deposition impacts the faradaic efficiency for CO by as much as 50% at 200 mA cm–2. Moreover, the solvent modulates the surface area, hydrophobicity, and capillarity of GDE catalyst layers. By measuring the hydrodynamic radii of catalyst inks, we conclude that solvent-mediated ionomer aggregation is a key factor that affects the microstructure and properties of GDE catalyst layers. We find that using ethanol as the ink solvent promotes moderate ionomer aggregation and yields the highest performing GDEs. This work describes the influence of electrode fabrication methodologies and demonstrates practical methods for preparing GDEs.