ac impedance study of the oxygen reduction mechanism on La_1-xSr_xMnO₃ in solid oxide fuel cells

The kinetics of the oxygen reduction reaction at the La0.85Sr0.15MnO3/ZrO2-Y2O3 electrode has been studied by ac impedance spectroscopy. The results show that there are three time constants present in the system, each one corresponding to a rate limiting step of the total reaction mechanism. The time constant at high frequencies has been attributed to the charge transfer of oxide ions from the interface electrode/electrolyte to oxide ion vacancies in the electrolyte.

The two other time constants, at medium frequencies and low frequencies, have been attributed to O2−2 dissociation and diffusion steps, respectively.