Study of the oxygen reduction reaction on pure and Zr-doped YMnO3+δ SOFC electrode

MORENO BOTELLO, ZULMA L.; ALEJANDRA MONTENEGRO-HERNÁNDEZ; MOGNI, LILIANA; GAUTHIER, GILLES H.

ELECTROCHIMICA ACTA

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2021 vol. 365

0013-4686

The effect of Zr-doping on the novel SOFC cathode YMnO3 and its O2-Reduction Reaction (ORR) was studied using electrochemical impedance spectroscopy (EIS) as a function of temperature (500 < T < 800 °C) and the oxygen partial pressure (10−4 < pO2 < 1 atm). EIS technique allows identifying three processes controlling the ORR for each electrode, differentiated by their characteristic frequency, activation energies and pO2 dependence. High frequency contribution, only observed at 600°C for both electrodes, was attributed to oxygen ion transfer trough the electrode/electrolyte interface. In both electrodes, the Intermediate frequency contribution was described by a Gerischer impedance, related to a co-limiting process between oxygen ion diffusion and a surface process. However, whereas the EIS characteristics for YMnO3 can be explained by a surface process controlled by the electron transfer from oxide to O-adsorbed, it seems related for Y0.9Zr0.1MnO3 to the probability of finding a second free-surface site near to a diatomicintermediated for the O2 dissociation. These differences are in agreement with the improvement of theelectrical properties when YMnO3 is doped with Zr. The low frequency contribution became importantas pO2 decreased and temperature increased, and its characteristics would indicate a secondary surfaceprocess, co-limited with O2 gas diffusion for Y0.9Zr0.1MnO3 porous electrode