Turning CO2 into ethanol: enhancing electrochemical reduction through cu-doped electrodes

Abstract

The electrochemical reduction of CO2 to ethanol represents a sustainable alternative to recycle CO2 into a value-added product, yet achieving high selectivity and efficiency remains a challenge. This work explores Cu-based catalysts supported on SiO2 and ZrO2, with and without ZnO doping, for ethanol production in a continuous flow-cell system. Gas diffusion electrodes are fabricated using commercial catalysts with varying Cu loadings (5-10%) and ZnO contents (2-3.5%). Comprehensive characterization by XPS confirms the presence of Cu2+ and Zn2+ species, while SEM reveals that ZnO incorporation improves surface uniformity and aggregate distribution compared to undoped samples. Electrochemical tests demonstrate that 10% Cu on SiO2 achieves a Faradaic efficiency of 96% for ethanol at -3 mA cm-2, outperforming both doped catalysts and previously reported materials. However, efficiency declines at higher current densities, indicating a trade-off between selectivity and productivity. ZnO doping enhances C2+ product formation but does not surpass the undoped catalyst in ethanol selectivity. These results underline the importance of catalyst composition, support interactions, and operating conditions, and point to further optimization of electrode architecture and cell configuration to sustain high ethanol yields under industrially relevant conditions.