Electrochemical Oxidation of CO in a CO-CO2 System at the Interface of Ni Grid Electrode/YSZ Electrolyte

Abstract

The electrochemical oxidation of CO at a nickel grid electrode on YSZ single crystal electrolyte in a mixture of CO-CO2-Ar was studied by means of electrochemical impedance spectroscopy at 850degreesC. At open circuit potential, the shape of the impedance spectra was dependent on the ratio of partial pressure Of CO2 to CO in the gas mixture. At high PCO2/PCO ratio (high PO2), the impedance diagram revealed at least two relaxation times whereas, it exhibited a simplest shape when the PCO2/PCO ratio was low (low PO2). Impedance spectra were modelled using an equivalent circuit describing the involvement of two adsorbed species during the oxidation of CO. The interface conductivity, sigma(p), value was dependent on both CO and CO2 partial pressures in the mixture. All these observations led us to suggest that CO, O, and Co-2 participate in the reaction mechanism where CO and O are in adsorbed form.