Liang, H. Q., Zhao, S., Hu, X. M., Ceccato, M., Skrydstrup, T. & Daasbjerg, K.
Cu is in the spotlight as it represents the only metal capable of catalyzing CO2 reduction to multicarbon products. However, its catalytic performance is determined collectively by a number of parameters including its composition and structure, electrolyte, and cell configuration. It remains a challenge to disentangle and understand the individual effect of these parameters. In this work, we study the effect of the electrode–electrolyte interface on CO2 reduction in water by coating CuO electrodes with polymers of varying hydrophilicities/phobicities. Hydrophilic polymers such as poly(vinyl alcohol) and poly(vinylpyrrolidone) exert negligible influence, while hydrophobic polymers such as poly(vinylidene fluoride) and polyethylene significantly enhance the activity, selectivity, and stability of CuO-derived electrodes toward C2H4 production. From ex situ characterizations, electrolysis in deuterated water, and molecular dynamics simulations, we propose that the improved catalytic performance triggered by hydrophobic polymers originates from restricted water diffusion and a higher local pH near the electrode surface. These observations shed light on interfacial manipulation for promoted CO2-to-C2H4 conversion.