Cyclic voltammetry of (La,Sr)MnO₃ electrode on YSZ substrate

The cyclic voltammograms of strontium-doped lanthanum manganite (LSM) electrode as a function of temperature, oxygen partial pressure and potential scan rate were investigated in this study. The current peaks corresponding to the reduction of LSM electrode materials and oxygen on the LSM surface were observed in the forward and backward scan. The electrochemical process for the reduction of Mn³⁺ and the concomitant formation of oxygen vacancies is reversible (or quasi-reversible), which has become irreversible at low temperature or fast scan rate. The improvement of LSM electrode performance under cathodic polarization and its gradual degradation after removal of applied potential were found to be related to two sequential reactions: reduction of Mn³⁺ to Mn²⁺ and recombination of Mn ²⁺ with the formed oxygen vacancies in the presence of oxygen. The oxygen reduction processes are strongly dependent on oxygen vacancies on the LSM electrode surface, which extend the reaction zone for oxygen reduction from three-phase boundary (TPB) to its vicinity under cathodic polarization.