Cyclic voltammetry characterization of a La_(0.8)Sr _(0.2)Co_(0.2)Fe_(0.8)O_(3 - δ) electrode interfaced to CGO/YSZ

摘要

The electrochemical characteristics of a La_(0.8)Sr _(0.2)Co_(0.2)Fe_(0.8)O_(3 - δ) cathode electrode interfaced to the CGO layer of a double layer CGO/YSZ electrolyte were studied using cyclic voltammetry, at temperatures of 600 to 850 °C and under oxygen partial pressures ranging from 0.07 to 21 kPa. The aim was to identify the electrochemical processes taking place under cathodic polarization on the basis of differences in the features of the cyclic voltammograms with changing conditions. Depending on temperature, sweep rate and oxygen partial pressure, current peaks appeared both in the forward and backward scans. Furthermore, reversed hysteresis was observed, i.e. higher currents in the backward scan than in the forward scan, with increasing oxygen partial pressure and decreasing temperature. The observed behavior was related to the electrochemical redox of B-sites and concomitant stoichiometry change as well as to the competing reaction of electrochemical oxygen redox, taking also into account the competitive action of chemical reactions occurring in the presence of gaseous oxygen.