Issue 42, 2014

Structure and properties of MgMxCr2−xO4 (M = Li, Mg, Ti, Fe, Cu, Ga) spinels for electrode supports in solid oxide fuel cells

Abstract

Novel electrode scaffold materials based on chromium-rich spinels, such as MgMxCr2−xO4, (M = Li, Mg, Ti, Fe, Cu, Ga) have been investigated for solid oxide fuel cell (SOFC) applications, in terms of conductivity and chemical stability when operated in fuel environments. Cation distributions were obtained by Rietveld refinement from X-ray diffraction data (XRD), with cation site preference considered in agreement with literature, and correlated with electrical properties determined experimentally. The substitutions with cations such as Li and Cu on B site improved the conductivity of the materials in air, while introducing Fe and Ga in the structure led to a decrease in conductivity in air. However, Fe had a positive contribution under reducing conditions, generating a change in the conductivity mechanism from p-type in air, to n-type. Conductivity measurements indicated that MgFexCr2−xO4 spinels exhibit faster reduction kinetics, in comparison with other substituted cations at the B site which is desirable in fuel cell application, for a reasonably fast response of a cell or a stack to reach its full functional potential. MgFeCrO4 showed fast reduction kinetics, with increase of the conductivity in reducing conditions from 0.014 S cm−1 to 0.4 S cm−1 and equilibration time for reaching the maximum conductivity value of 10 hours, under dry 5% H2/Ar at 850 °C.

Graphical abstract: Structure and properties of MgMxCr2−xO4 (M = Li, Mg, Ti, Fe, Cu, Ga) spinels for electrode supports in solid oxide fuel cells

Article information

Article type
Paper
Submitted
15 Jul 2014
Accepted
18 Sep 2014
First published
19 Sep 2014

J. Mater. Chem. A, 2014,2, 18106-18114

Author version available

Structure and properties of MgMxCr2−xO4 (M = Li, Mg, Ti, Fe, Cu, Ga) spinels for electrode supports in solid oxide fuel cells

E. Stefan, P. A. Connor, A. K. Azad and J. T. S. Irvine, J. Mater. Chem. A, 2014, 2, 18106 DOI: 10.1039/C4TA03633F

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