(Invited) Titanate-Based Electrodes for Solid Oxide Cells

Abstract

This talk describes solid oxide cell electrodes based on Sr(Ti0.3Fe0.7)O3 (STF). For oxygen electrodes, the substitution of a small amount of Co (up to 15%) for Fe substantially reduces polarization resistance, e.g., from 0.7 to 0.2 Wcm2in air at 600 oC.[1] The oxygen transport rate coefficients and polarization resistance RP values are increased by a factor of ~ 3 times by Co substitution, and are generally much better than those for the widely used (La,Sr)(Co,Fe)O3 electrodes. Electrode and cell stability are markedly improved compared to LSCF cathodes. PrOxinfiltration into Co-substituted STF yields a substantial reduction in RP , to values useful for low-temperature (<600 oC) solid oxide cells. For fuel electrodes, Sr(Ti0.3Fe0.7)O3 yields good performance at ≥ 800 oC and hydrogen-rich fuels, but the performance suffers at lower temperature and in depleted fuel due to slow H2 dissociative adsorption.[2] The substitution of 7% Ni for Fe in Sr deficient STF substantially reduces RP under these conditions.[3] The Ni substitution results in the exsolution of Ni and Fe from the perovskite, yielding Ni-Fe nanoparticles that decorate the oxide electrode surfaces and promote hydrogen dissociative adsorption. Perovskite stoichiometry, which changes during exsolution, is found to play an important role in electrode performance; initially Sr-deficient anodes yield much lower RP values. RP values for Ni-substituted STF are comparable those of Ni-YSZ anodes. References：[1] S.-L. Zhang, H. Wang, M.Y. Lu, A.-P. Zhang, L.V. Mogni, Q. Liu, C.-X. Li, C.-J. Li, S.A. Barnett, Energy & Environmental Science (2018, DOI: 10.1039/C8EE00449H). [2] T. Zhu, D.E. Fowler, K.R. Poeppelmeier, M. Han, S.A. Barnett, Journal of The Electrochemical Society 163 (2016) (8) F952. [3] T. Zhu, H.E. Troiani, L.V. Mogni, M. Han, S.A. Barnett, Joule (2018) 10.1016/j.joule.2018.02.006.