Electrochemical reduction of CO2 using oxide based Cu and Zn bimetallic catalyst

Abstract

Electrochemical reduction of carbon dioxide (ERCO2) driven by non-conventional sources of energy is a favorable approach to generate closed loop CO2 cycle. It will reduce CO2 emissions by lowering CO2 levels in the atmosphere and converting it into high-energy-density carbon-based fuels like alcohols and hydrocarbons. Monometallic copper based catalysts are largely reported for ERCO2 to a variety of industrially important carbon products. But, challenges such as high over potential, uncontrollable product selectivity, and catalyst deactivation inhibit their progress. Oxide derived bimetallic CuZnx electrocatalysts have been suggested as alternatives for achieving high selectivity for different valuable products. In this study, the co-precipitation approach has been used to prepare CuO with various quantities of ZnO dopants. HRTEM, FESEM, XRD, and XPS were used to conduct detailed morphological and elemental studies on the electrode. The electrochemical performance was measured using H-type electrochemical cell in aqueous 0.1 M KHCO3 electrolyte. The evaluation of different CuO-ZnOx (where x=5, 10, 15 and 20 wt.%) catalysts for ethanol productivity and Faradaic efficiency are of particular importance. Amongst studied electrocatalysts, the highest Faradaic efficiency of 22.27 % was obtained for ethanol using CuO-ZnO10 at -0.80 V (vs RHE) with the production rate of about 121 µmol h−1 L−1. The optimized electrode (CuO-ZnO10) shows long term stability for at least 12 h. Post characterization of the catalyst was also conducted to obtain an insight into the active sites, which indicated that CO2 reduction took place on reduced oxide sites (i.e. metallic sites) rather than metal oxides.