Back to Search Start Over

Lanthanum doped strontium titanate - ceria anodes: deconvolution of impedance spectra and relationship with composition and microstructure.

Lanthanum doped strontium titanate - ceria anodes: deconvolution of impedance spectra and relationship with composition and microstructure.

Authors :
Burnat, Dariusz
Nasdaurk, Gunnar
Holzer, Lorenz
Kopecki, Michal
Heel, Andre
Source :
Journal of Power Sources. May2018, Vol. 385, p62-75. 14p.
Publication Year :
2018

Abstract

Electrochemical performance of ceramic (Ni-free) SOFC anodes based on La 0.2 Sr 0.7 TiO 3-δ (LST) and Gd 0.1 Ce 0.9 O 1.95-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. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
03787753
Volume :
385
Database :
Academic Search Index
Journal :
Journal of Power Sources
Publication Type :
Academic Journal
Accession number :
128718626
Full Text :
https://doi.org/10.1016/j.jpowsour.2018.03.024