Reduction of carbon dioxide in 3-dimensional gas diffusion electrodes

Experiments on the electrochemical reduction of CO2 were carried out by using a Cu/PTFE-bonded gas diffusion electrode (GDE) to investigate the effect of solvents, Cu/C ratio and electrolyte concentration on the characteristics of reduction products. The experimental conditions were a voltage range from -2.0 to -3.5 V vs. saturated calomel electrode (SCE) and electrolyte concentration from 0.1 M to 0.5 M. Significant performance differences were found between water and organic solvent (isobutanol+EtOH). The GDE was more active with water than that with organic solvent. And then, in the case of the Cu/PTFE-bonded gas diffusion electrode using organic solvent, the maximum faradaic efficiencies of reduction products were achieved in a Cu/C ratio of 0.5. The faradaic efficiency of C2H4 among the reduction products decreased as the Cu/C ratio increased; whereas, those of CO and alcohol increased. Since the difference in pH at the electrode influences the variation of product selectivity, the faradaic efficiency of C2H4 might increase due to the pH increase caused by electrolyte concentration difference.