Effect of Electrolyte on the Electrochemical Reduction of CO2

Electrochemical experiments were carried out in a laboratory-made, divided H-type cell to study the electrochemical reduction of CO2. A copper wire, Ag/AgCl electrode and Pt wire were used as the working, reference and counter electrode, respectively. A potential ramp between 0 and -1.2 V was applied to the cell and the current was monitored as a function of potential. The effect of the electrolyte on the electrochemical reduction of CO2 was investigated by using NaHCO3 and KHCO3. It was observed that the latter electrolyte favored higher currents. This may be related to the cation size and electro negativity. The role of the electrolyte in this reaction may be explained by assuming that CO2 bonds to HCO3- and K+, generating intermediate specie prior to its electrochemical reduction. This would explain that the current increased as a function of KHCO3 concentration. The insertion of CO2 between the anion and the cation is a very important step in the electrochemical reaction. The formation of a new HCO3-C bond results in the weaking of C-O bond and the activation of CO2 occurs. The electron transfer from the electrode to the CO2 is facilitated.