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

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

ELECTROCHIMICA ACTA

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2021 vol. 385 p. 137332 - 137342

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 ºC) 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  diatomic intermediated  for  the  O2 dissociation.  These  differences  are  in  agreement  with  the improvement of the electrical properties when YMnO3 is doped with Zr. The low frequency contribution  became  important  as  pO2 decreased  and  temperature  increased,  and  its characteristics  would  indicate  a  secondary  surface  process,  co-limited  with  O2 gas diffusion for Y0.9Zr0.1MnO3 porous electrode