Oxygen Reduction Reaction on Ruddlesden-Popper Phases Studied by Impedance Spectroscopy
L. MOGNI; N. GRUNBAM; F. PRADO; A. CANEIRO
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
ELECTROCHEMICAL SOC INC
Año: 2011 vol. 152 p. 202 - 202
The oxygen reduction mechanism of Ruddlesden?Popper phases Sr3FeMO6+ M = Fe, Co, Ni has been investigated by impedancespectroscopy at 500, 600, and 700°C under oxygen partial pressure pO2 between 10−5 and 1 atm using both He and Ar as gascarriers. Thick porous electrodes were sprayed on dense Ce0.9Gd0.1O2−x and impedance spectra data were collected on symmetricalcells. An equivalent circuit was proposed considering the electrolyte resistances Rel, a Warburg element WHF, and two parallelelements RCpe RCpeIF and RCpeLF. For the three compounds, WHF has been assigned to the oxygen vacancies diffusion in thebulk, the intermediate component, RCpeIF, to oxygen dissociative adsorption in the electrode surface, and the low frequencyelement, RCpeLF, to oxygen diffusion in the gas phases. In the case of the Sr3Fe2O6+ and Sr3FeCoO6+ compounds, the pO2dependence of Warburg high frequency component suggests a complex process involving both oxygen bulk diffusion and chargetransfer. The results of Sr3FeMO6+ M = Fe, Co, Ni compared with those of La0.6Sr0.4Co0.8Fe0.2O3− perovskite electrodes,allowing us to discuss the effect of the crystal structure on the electrochemical behavior of these layered compounds.