La/Ba-based cobaltites as IT-SOFC cathodes: a discussion about the effect of crystal structure and microstructure on the O2-reduction reaction. (10th October 2016)

• Record Type: Journal Article
• Authors: Garcés, Diana; Soldati, Analia L.; Troiani, Horacio; Montenegro-Hernández, Alejandra; Caneiro, Alberto; Mogni, Liliana V.
• Is Part Of: Electrochimica acta. Volume 215(2016)
• Page Start: 637
• Page End: 646
• Publication Date: 2016-10-10
• Subjects: IT-SOFC -- perovskite -- cathode -- O2-reduction reaction -- LBC; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2016.08.132
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: This work discusses the effect of the crystal structure and microstructure on the electrocatalytic activity of Lanthanum-Barium cobaltite (LBC), evaluatedas IT-SOFC cathode. Two systems with similar microstructures (particle sizes dp ≈ 1–5 μm) are used to compare the effect of the crystal structure: the cubic La0.5 Ba0.5 CoO3-δ with La/Ba cations randomly distributed, and a tetragonal LaBaCo2 O6-δ with La/Ba layered distribution. In addition, the effect of microstructure is studied by using a newsol-gel route which allows obtaining LaBaCo2 O6-δ with smallest particle size (dp ≈ 500 nm). The electrode reaction isstudied by electrochemical impedance spectroscopy (EIS) as a function of temperature (T) and oxygen partial pressure (pO2 ). The electrode polarization resistance (RC, P ) presents two contributions, a low frequency (RLF ) and a high frequency Gerischer-resistance (RG ). On one side, RLF, associated to the O2 -gas diffusion across the gas layer boundary, presents low activation energy (Ea ) and is proportional to pO2 −1, presenting the same values regardless the microstructure.On the other side, RG is in agreement with anO2 -reduction mechanismco-limited by O-surface exchange and O-bulk diffusion. RG is strongly influenced by structure (trough the diffusion coefficient DV ) and microstructure (inversely proportional to dp ). Besides, RG decreases by reducing dp and by modifying the La/Ba ordering from layered to randomly distributed.