Research output: Contribution to journal › Article › peer-review
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 language | English |
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Journal | Faraday Discussions |
Early online date | 8 Apr 2015 |
DOIs | |
Publication status | Published - 2015 |
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