Title: Lanthanum doped strontium titanate - ceria anodes : deconvolution of impedance spectra and relationship with composition and microstructure
Authors : Burnat, Dariusz
Nurk, Gunnar
Holzer, Lorenz
Kopecki, Michal
Heel, Andre
Published in : Journal of Power Sources
Volume(Issue) : 385
Pages : 62
Pages to: 75
Publisher / Ed. Institution : Elsevier
Issue Date: May-2018
License (according to publishing contract) : Licence according to publishing contract
Type of review: Peer review (Publication)
Language : English
Subjects : SOFC; Titanates LST; Microstructure analysis; Electrochemical Impedance Spectroscopy; Redox; Anodes
Subject (DDC) : 540: Chemistry
621.3: Electrical engineering and electronics
Abstract: Electrochemical performance of ceramic (Ni-free) SOFC anodes based on La0.2Sr0.7TiO3-δ (LST) and Gd0.1Ce0.9O1.95-δ (CGO) is thoroughly investigated. Microstructures and compositions are systematically varied around the percolation thresholds of both phases by modification of phase volume fractions, particle size distributions and firing temperature. Differential impedance spectroscopy was performed while varying gas composition, electrical potential and operating temperature, which allows determining four distinct electrode processes. Significant anode impedances are measured at low frequencies, which in contrast to the literature cannot be linked with gas concentration impedance. The dominant low frequency process (∼1 Hz) is attributed to the chemical capacitance. Combined EIS and microstructure investigations show that the chemical capacitance correlates inversely with the available surface area of CGO, indicating CGO surface reactions as the kinetic limitation for the dominant anode process and for the associated chemical capacitance. In anodes with a fine-grained microstructure this limitation is significantly smaller, which results in an impressive power output as high as 0.34 Wcm−2. The anodes show high redox stability by not only withstanding 30 isothermal redox cycles, but even improving the performance. Hence, compared to conventional Ni-cermet anodes the new LST-CGO material represents an interesting alternative with much improved redox-stability.
Departement: School of Engineering
Organisational Unit: Institute of Computational Physics (ICP)
Institute of Materials and Process Engineering (IMPE)
Publication type: Article in scientific Journal
DOI : 10.1016/j.jpowsour.2018.03.024
ISSN: 0378-7753
1873-2755
URI: https://digitalcollection.zhaw.ch/handle/11475/8923
Appears in Collections:Publikationen School of Engineering

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