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Effects of trivalent dopants on phase stability and catalytic activity of YBaCo4O7-based cathodes in solid oxide fuel cells

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Abstract

In order to understand the doping and co-doping effects of trivalent cations (Al3+, Ga3+, and Fe3+) in the swedenborgite oxide YBaCo4O7 as a cathode in intermediate-temperature solid oxide fuel cells (IT-SOFCs), four series of YBaCo4O7-based materials, including YBaCo4−xAlxO7+δ, YBaCo4−xyGaxAlyO7+δ, YBaCo3.2Ga0.8−xFexO7+δ, and YBaCo3.5−xAl0.5FexO7+δ, have been synthesized and investigated. The long-term phase stability has been evaluated by X-ray diffraction after the samples were annealed at 600–800 °C under ambient air for 120 h. Although Al has been suggested to have better phase stabilization capability than Ga in the literature, severe decomposition above 700 °C occurs in all the YBaCo4−xAlxO7+δ samples. Fe has much weaker phase stabilization capability than Al and Ga, but excellent phase stability is still maintained with a small substitution of Fe for Ga. All the materials with a stable phase at high temperatures exhibit well-matched thermal expansion coefficients (8.0–9.5 × 10−6 K−1) with common electrolyte materials, which alleviates the thermal stress during the SOFC operation. In comparison to YBaCo3.2Ga0.8O7+δ, a partial substitution of Ga by Fe enhances the catalytic activity for the oxygen reduction reaction. In addition, the performance of the anode-supported single cell with the YBaCo3.2Ga0.7Fe0.1O7–Ce0.8Gd0.2O1.9 composite cathode reached 1.0 W cm−2 with H2 fuel at 700 °C. Thus, this work provides a guideline on trivalent dopants for developing swedenborgite-based cathode materials with a high phase stability and catalytic activity in IT-SOFCs.

Graphical abstract: Effects of trivalent dopants on phase stability and catalytic activity of YBaCo4O7-based cathodes in solid oxide fuel cells

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Publication details

The article was received on 05 Feb 2018, accepted on 27 Jul 2018 and first published on 27 Jul 2018


Article type: Paper
DOI: 10.1039/C8TA01230J
Citation: J. Mater. Chem. A, 2018, Advance Article
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    Effects of trivalent dopants on phase stability and catalytic activity of YBaCo4O7-based cathodes in solid oxide fuel cells

    K. Lai and A. Manthiram, J. Mater. Chem. A, 2018, Advance Article , DOI: 10.1039/C8TA01230J

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