Conductivity and stability of cobalt pyrovanadate |
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Authors: | Peter I. Cowin Rong LanChristophe T.G. Petit Lei ZhangShanwen Tao |
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Affiliation: | a Department of Chemical and Process Engineering, University of Strathclyde, Glasgow, G1 1XJ, UK b Department of Chemistry, Heriot-Watt University, Edinburgh, EH14 4AS, UK |
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Abstract: | Cobalt pyrovanadate was successfully synthesised by a solid state route and the conductivity in both oxidising and reducing environments was determined for the first time. Impedance measurements between 300 °C and 700 °C in air determined that Co2V2O7 is an intrinsic semiconductor with activation energy of 1.16(3) eV. The conductivity in air reached a maximum of 4 × 10−4 S cm−1 at 700 °C. Semiconducting behaviour was also observed in 5% H2/Ar, albeit with a much smaller activation energy of 0.04(4) eV. Between 300 °C and 700 °C the conductivity ranged from 2.45 S cm−1 to 2.68 S cm−1, which is approaching the magnitude required for SOFC anode materials. Thermogravimetric analysis found a significant weight loss upon reduction of the compound. X-ray diffraction analysis, coupled with data from previous research, suggested compound degradation into Co2−xV1+xO4, CoO and VO. The redox instability and the low conductivity lead us to the conclusion that cobalt pyrovanadate is unsuitable for utilisation as an anode material for SOFCs although the conductivity is reasonable in a reducing atmosphere. |
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Keywords: | Conductivity Cobalt pyrovanadate Anode Solid oxide fuel cell |
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