Kinetic Study of the Formation of Oxygen Vacancy on Lanthanum Manganite Electrodes

The electrochemical reduction of oxygen on Lanthanum Manganite(LSM) electrodes has been investigated by cyclic voltammetry, AC impedance and, in particular, potential step. An emphasis was given to the study of the kinetics of the formation of oxygen vacancy, which is shown to be the main cause for the reserved hysteresis in cyclic voltammograms and for the increase in the electrochemical activity of oxygen reduction on the cathodically polarized LSM electrode both observed in AC impedance and in potential step experiments. The potential step experiments show that the oxygen vacancy concentration increases exponentially with time when the LSM is under a cathodic polarization. In the presnet study, the rate controlling step for the formation of oxygen vacancies is oxygen vacancy generation step. The cathodic current rising from the reaction on oxygen vacancies can make a significant contribution to the total reduction current.