Degradation of oxygen reduction reaction kinetics in porous La0.6Sr0.4Co0.2Fe0.8O3-δ cathodes due to aging-induced changes in surface chemistry

JOURNAL OF POWER SOURCES

卷:337

Article

Baque, Laura C.¹  Soldati, Analia L.¹  Teixeira-Neto, Erico²  Troiani, Horacio E.¹  Schreiber, Anja³  Serquis, Adriana C.¹ 

[1] Ctr Atom Bariloche, CNEA, CONICET, Ave Bustillo 9500,R8402AGP, San Carlos De Bariloche, Argentina

[2] Brazilian Ctr Res Energy & Mat, Brazilian Nanotechnol Natl Lab, Rua Giuseppe Maximo Scolfaro 10-000, Campinas, SP, Brazil

[3] Deutsch GeoForschungsZentrum GFZ, Helmholtz Zentrum Potsdam, Sekt Geomech & Rheol 4 2, C 155, D-14473 Potsdam, Germany

关键词: Solid Oxide Fuel Cells;    Degradation;    Surface segregation;    Scanning Transmission Electron Microscopy;    Energy Dispersive Spectroscopy;    Electrochemical Impedance Spectroscopy;   

DOI  :  10.1016/j.jpowsour.2016.10.090

来源: Elsevier

【 摘 要 】

The modification of surface composition after long-term operation is one of the most reported degradation mechanisms of (La,Sr)(Co,Fe)O3-delta (LSCFO) cathodes for Solid Oxide Fuel Cells (SOFCs). Nevertheless, its effect on the oxygen reduction reaction kinetics of porous LSCFO cathodes has not been yet reliably established. In this work, La- and Sr-enrichment at the LSCFO surface of porous cathodes has been induced after 50 h aging at 800 degrees C under air. Such cation redistribution can extend up to -400 nm depth under the LSCFO surface as detected by high resolution Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy maps acquired inside the cathode pores. The observed surface chemical changes hamper the oxygen surface exchange reaction at the LSCFO/gas interface. Accordingly, a suitable Electrochemical Impedance Spectroscopy analysis revealed that the oxygen ion conductivity remains practically unaltered during the aging treatment while the oxygen surface exchange resistance increases up to 1.8 times. As a result, the cathode impedance response deteriorates within the 10-0.1 Hz frequency range during the aging treatment, resulting in a total cathode area specific resistance increase of 150%. The methodology adopted has demonstrated to be very valuable for studying the degradation of SOFC cathodes produced by the modification of surface composition. (C) 2016 Elsevier B.V. All rights reserved.

【 授权许可】

Free