Impedance Analysis of Oxygen Reduction in Lithium Carbonate Melt: Effect of Partial Pressure of Carbon Dioxide

Effects of partial pressure of CO2 and temperature on oxygen reduction kinetics in lithium carbonate melt were examined using electrochem. impedance spectroscopy (EIS) and cyclic voltammetry. The impedance spectra were analyzed by a complex nonlinear least-squares (CNLS) method, using the Randles-Ershler equivalent circuit model, to estimate the electrode kinetic and mass transfer parameters, such as the charge transfer resistance and Warburg coefficient The cyclic voltammetric measurements indicated that the oxygen reduction process in lithium carbonate melt is "reversible" up to 200 mV/s. Values of the diffusion parameter, D01/2CO determined by cyclic voltammetry concurred with those estimated by EIS method. The reaction order with respect to carbon dioxide and the activation energy for the exchange c.d. were determined to be -0.52 and 132 kJ/mol, resp. Also, the reaction order with respect to carbon dioxide and the activation energy for DO1/2COwere calculated to be -0.8 and 185 kJ/mol, resp.