CO2 attraction by specifically adsorbed anions and subsequent accelerated electrochemical reduction
By Ogura, Kotaro; Ferrell III, Jack R.; Cugini, Anthony V.; Smotkin, Eugene S. & Salazar-Villalpando, Maria D.
Published in Electrochimica Acta
2010
Abstract
The electrochemical reduction of CO2 was studied on a copper mesh electrode in aqueous solutions containing 3 M solutions of KCl, KBr and KI as the electrolytes in a two and three phase configurations. Electrochemical experiments were carried out in a laboratory-made, divided H-type cell. The working electrode was a copper mesh, while the counter and reference electrodes were Pt wire and Ag/AgCl electrode, respectively. Results of our work suggest a reaction mechanism for the electrochemical reduction of CO2 in the two phase configuration where the presence of Cu-X as the catalytic layer facilitates the electron transfer from the electrode to CO2. Electron-transfer to CO2 may occur via the Xad-(Br-, Cl-, I-)–C bond, which is formed by the electron flow from the specifically adsorbed halide anion to the vacant orbital of CO2. The stronger the adsorption of the halide anion to the electrode, the more strongly CO2 is restrained, resulting in higher CO2 reduction current. Furthermore, it is suggested that specifically adsorbed halide anions could suppress the adsorption of protons, leading to a higher hydrogen overvoltage. These effects may synergistically mitigate the overpotential necessary for CO2 reduction, and thus increase the rate of electrochemical CO2 reduction.