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

JOURNAL OF POWER SOURCES

卷:385

Article

Burnat, Dariusz¹  Nurk, Gunnar²  Holzer, Lorenz³  Kopecki, Michal⁴  Heel, Andre¹ 

[1] Zurich Univ Appl Sci, Inst Mat & Proc Engn, CH-8401 Winterthur, Switzerland

[2] Univ Tartu, Inst Chem, Ravila 14a, EE-50411 Tartu, Estonia

[3] Zurich Univ Appl Sci, Inst Computat Phys, CH-8401 Winterthur, Switzerland

[4] AGH Univ Sci & Technol, Dept Ceram & Refractories, PL-30059 Cracov, Poland

关键词: SOFC;    LST;    Microstructure analysis;    Electrochemical impedance;    Spectroscopy;    Redox;    Anodes;   

DOI  :  10.1016/j.jpowsour.2018.03.024

来源: Elsevier

【 摘 要 】

Electrochemical performance of ceramic (Ni-free) SOFC anodes based on La0.2Sr0.7TiO3.delta (LST) and Gd0.1Ce0.9O1.95.delta (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 (similar to 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.

【 授权许可】

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