A Hybrid Catalyst-Bonded Membrane Device for Electrochemical Carbon Monoxide Reduction at Different Relative Humidities

A hybrid catalyst-bonded membrane device using gaseous reactants for carbon monoxide reduction (COR) reaction in the cathode chamber, an aqueous electrolyte for oxygen evolution reaction (OER) in the anode chamber, and an anion exchange membrane (AEM) for product separation was constructed. The Cu electrocatalyst was electrodeposited onto the gas diffusion layers (GDLs) and was directly bonded to the AEM by mechanical pressing in the test-bed. The impacts of relative humidity at the cathode inlet on the selectivity and activity of COR were investigated by computational modeling and experimental methods. At a relative humidity of 30%, the Cu-based catalyst in the hybrid device exhibited a total operating current density of 87 mA cm^(-2) at -2.0 V vs. Ag/AgCl reference electrode, a Faradaic Efficiency (FE) for C_2H_4 generation of 32.6%, and an FE for liquid-based carbon product of 42.6%. Significant improvements in the partial current densities for COR were observed in relative to planar electrodes or flooded gas diffusion electrodes (GDEs). In addition, a custom test-bed was constructed to characterize the oxidation states of the Cu catalysts in real time along with product analysis though the backside of the GDLs via operando X-ray absorption (XAS) measurements.