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• 作者：Ke-Yu LaiArumugam Manthiram
• 刊名：Chemistry of Materials
• 出版年：2016
• 出版时间：December 27, 2016
• 年：2016
• 卷：28
• 期：24
• 页码：9077-9087
• 全文大小：847K
• ISSN：1520-5002

文摘

With an aim of enhancing their high-temperature phase stability, oxygen-storage capability, and electrocatalytic activity in intermediate-temperature solid oxide fuel cells (IT-SOFCs), RBaCo4O_7+δ-based samples have been investigated with a co-substitution at the R site with Y, In, and Ca and Ga substitution at the Co site. YBaCo_4–yGa_yO_7+δ, Y_1–xIn_xBaCo_3.3Ga_0.7O_7+δ, Y_1–xCa_xBaCo_3.3Ga_0.7O_7+δ, In_1–xCa_xBaCo_3.3Ga_0.7O_7+δ, and Y_0.5In_0.5BaCo_4–yGa_yO_7+δ series of materials have been synthesized by a solid-state reaction, and the phase stabilities have been assessed by long-term testing at 600–800 °C for 120 h. The substitution of In for Y mitigates the phase decomposition but decreases the oxygen-storage capacity and electrochemical performance in IT-SOFCs. With In and Y co-dopants, Y_0.5In_0.5BaCo_3.5Ga_0.5O_7+δ remains stable even with a smaller amount of Ga. In contrast, Ca doping reduces the phase stability regardless of its content. Via optimization of the compositions, Y_0.9In_0.1BaCo_3.3Ga_0.7O_7+δ is found to exhibit the best electrochemical performance without decomposition in the long-term test at 600–800 °C. The anode-supported single cell with the Y_0.9In_0.1BaCo_3.3Ga_0.7O_7+δ + GDC composite cathode reaches a maximum power density of 0.91 W cm^–2 at 700 °C, which is the highest reported for this class of materials. Moreover, the ideal matching of the relatively low thermal expansion coefficient of Y_0.9In_0.1BaCo_3.3Ga_0.7O_7+δ (7.5–9.2 × 10^–6 K^–1) with those of common electrolytes alleviates the thermal stress during long-term operation in IT-SOFCs. The combination of long-term phase stability, high oxygen-storage capability, and electrocatalytic properties makes the Y_0.9In_0.1BaCo_3.3Ga_0.7O_7+δ + GDC composite cathode appealing for practical application in IT-SOFCs.