Electroreduction of CO2 using Cu/Zn oxides loaded gas diffusion electrodes

Gas diffusion electrodes (GDEs) consist of a gas layer (mixture of hydrophobic carbon black (CB phob ) and PTFE dispersion) and a reaction layer (mixture of catalyst powder, CB phob , hydrophilic CB (CB phil ), and PTFE) laminated on a Cu mesh as a current collector. As the catalyst, CuO/ZnO (3:7 by mole ratio) mixed oxides and a mixture of a Cu powder (4N, -325 mesh) and a ZnO powder were examined. Electroreduction was performed potentiostatically passing in general 200 C using a W -shaped Pyrex cell having one gas and two liquid chambers, with two lines of gas circulating systems. When using a GDE of (CuO / ZnO = 3 / 7 : CB = 6 : 5 [by weight], the reduction products were mainly C 2 H 5 OH with slight amounts of CO and HCOO - , and a comparable amount of H 2 . Faradaic efficiency maximum of 16.7% for C 2 H 5 OH formation with maximum selectivity of 88% was observed at -1.32 V vs. Ag-AgCl, at a partial current density of 4.23 mA/cm 2 , which is about 50 times greater than that obtained on a sintered oxide electrode. In the case of the GDE of (Cu / ZnO = 3 : 7) : CB = 3 : 1 reduced by H 2 , the selectivity of the reduction products became poorer, like in the case of a Cu foil electrode, with lower current density, although the total faradaic efficiencies for CO 2 reduction was 40.5% with additional formation of n-C 3 H 7 OH and C 2 H 4 at -1.30 V.