Calcium manganite as oxygen electrode materials for reversible solid oxide fuel cell

Chengsheng Ni, John T.S. Irvine

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Abstract

For an efficient high-temperature reversible solid oxide fuel cell (RSOFC), the oxygen electrode should be highly active for the conversion between oxygen anions and oxygen gas. CaMnO3-δ(CM) is a perovskite that can be readily reduced with the formation of Mn3+ giving rise to oxygen defective phases. CM is examined here as the oxygen electrode for a RSOFC. CaMn0.9Nb0.1O3-δ (CMN) with Nb doping shows superior electric conductivity (125 S cm-1 at 700 ºC) to CM (1-5 S cm-1 at 700 ºC) in air and is also examined for comparison. X-ray diffraction (XRD) data show that CM and CMN are compatible with the widely used yttria-stabilized zirconia (YSZ) electrolyte up to 950 oC. Both materials show a thermal expansion coefficient (TEC) close to 10.8-10.9 ppm K-1 in the temperature range between 100-750 ºC, compatible with that of YSZ. Polarization curves and electrochemical impedance spectra for both fuel cell and steam electrolysis modes were investigated at 700 ºC, showing that CM presented a polarization resistance of 0.059 Ωcm2 under a cathodic bias of -0.4 V while CMN gave a polarization resistance of 0.081 Ω cm2 under an anodic bias of 0.4 V. The phase stability up to 900 ºC of these materials was investigated with thermogravimetric analysis (TGA) and variable temperature XRD.

Original languageEnglish
JournalFaraday Discussions
Early online date8 Apr 2015
DOIs
Publication statusPublished - 2015

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