When Flooding Is Not Catastrophic─Woven Gas Diffusion Electrodes Enable Stable CO₂ Electrolysis

Electrochemical CO₂ reduction has the potential to use excess renewable electricity to produce hydrocarbon chemicals and fuels. Gas diffusion electrodes (GDEs) allow overcoming the limitations of CO₂ mass transfer but are sensitive to flooding from (hydrostatic) pressure differences, which inhibits upscaling. We investigate the effect of the flooding behavior on the CO₂ reduction performance. Our study includes six commercial gas diffusion layer materials with different microstructures (carbon cloth and carbon paper) and thicknesses coated with a Ag catalyst and exposed to differential pressures corresponding to different flow regimes (gas breakthrough, flow-by, and liquid breakthrough). We show that physical electrowetting further limits the flow-by regime at commercially relevant current densities (≥200 mA cm^-2), which reduces the Faradaic efficiency for CO (FE_CO) for most carbon papers. However, the carbon cloth GDE maintains its high CO₂ reduction performance despite being flooded with the electrolyte due to its bimodal pore structure. Exposed to pressure differences equivalent to 100 cm height, the carbon cloth is able to sustain an average FE_CO of 69% at 200 mA cm^-2 even when the liquid continuously breaks through. CO₂ electrolyzers with carbon cloth GDEs are therefore promising for scale-up because they enable high CO₂ reduction efficiency while tolerating a broad range of flow regimes.