Oxygen reduction reaction in Pr2NiO4+δ/Ce0.9Gd0.1O1.95 and La0.6Sr0.4Co0.2Fe0.8O3−δ /La0.8Sr0.2Ga0.8Mg0.2O2.80 half cells: an electrochemical study

Benoit Philippeau (1) , Fabrice Mauvy (1) , Clément Nicollet (1) , Sébastien Fourcade (1) , Jean-Claude Grenier (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

The electrochemical properties of La0.6Sr0.4Co0.2Fe0.8O3−δ and Pr2NiO4+δ electrodes screen-printed on La0.8Sr0.2Ga0.8Mg0.2O2.8 and Ce0.9Gd0.1O1.95, respectively, have been investigated by electrochemical impedance spectroscopy (EIS). A study of the heat treatment of La0.6Sr0.4Co0.2Fe0.8O3−δ material used as oxygen electrode associated to La0.8Sr0.2Ga0.8Mg0.2O2.8 electrolyte was performed. The La0.6Sr0.4Co0.2Fe0.8O3−δ porous electrode sintered at 900 °C for 1 h in air exhibits the lowest cathodic polarization resistance; i.e. R P = 0.12 Ω cm2 at 600 °C. The SEM images show that the La0.6Sr0.4Co0.2Fe0.8O3−δ electrode structure is highly porous, facilitating the gas diffusion and maximizing the number of active sites for the oxygen reduction reaction (ORR). Furthermore, it forms good contact with the electrolyte after this heat treatment. In order to characterize the oxygen electrode reaction of La0.6Sr0.4Co0.2Fe0.8O3−δ and Pr2NiO4+δ , the electrochemical impedance spectroscopy (EIS) measurements were performed at temperatures between 400 and 700 °C and at different oxygen partial pressures (pO2) ranging in between 10−3 and 0.21 atm. Analysis of the impedance data revealed that there are two different processes involved in the cathode reaction. The first process in the medium-frequency range is assigned to the oxygen surface exchange reaction at the electrode/gas interface and possibly to the ionic diffusion in the material for La0.6Sr0.4Co0.2Fe0.8O3−δ and to the dissociation of the adsorbed molecular oxygen for Pr2NiO4+δ . The second one at low frequency is associated to the gas phase diffusion for both cathodes. The exchange current density, i 0, allows evaluating the electrocatalytic activity of the cathode materials. The La0.6Sr0.4Co0.2Fe0.8O3−δ /La0.8Sr0.2Ga0.8Mg0.2O2.8 couple shows the largest i 0 value, reaching 432 mA cm−2 at 700 °C and suggesting a high electrochemical activity for the O2 reduction reaction.

Mots clés: Praseodymium nickelate; Lanthanum strontium ferro-cobaltite; AC impedance spectroscopy; Oxygen electrode reaction; Exchange current density; SOFC cathode

Domaines: Autre

Benoit Philippeau, Fabrice Mauvy, Clément Nicollet, Sébastien Fourcade, Jean-Claude Grenier. Oxygen reduction reaction in Pr2NiO4+δ/Ce0.9Gd0.1O1.95 and La0.6Sr0.4Co0.2Fe0.8O3−δ /La0.8Sr0.2Ga0.8Mg0.2O2.80 half cells: an electrochemical study. Journal of Solid State Electrochemistry, 2015, 19 (3), pp.871-882. ⟨10.1007/s10008-014-2686-6⟩. ⟨hal-01122737⟩