Structural, electrical, and electrochemical properties of cobalt-doped NiFe₂O₄ as a potential cathode material for solid oxide fuel cells

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• 作者：Yuanyuan Rao ; Zhenbin Wang ; Long Chen ; Ruofei Wu ; Ranran Peng ; Yalin Lu
• 关键词：Spinel material ; Solid oxide fuel cell ; Electrical conductivity ; Single-phase electrode ; Cathode
• 刊名：International Journal of Hydrogen Energy
• 出版年：2013
• 出版时间：4 November, 2013
• 年：2013
• 卷：38
• 期：33
• 页码：14329-14336
• 全文大小：1909 K

文摘

In this work, Co-doped NiFe₂O₄ spinels (NFCO-x) are successfully fabricated and characterized as possible cathode materials for the intermediate-temperature solid oxide fuel cells (SOFC). Results of the binding energy calculations using the density functional theory suggest that the reverse spinel structure is stable when Co³⁺ occupies the octahedral interstitial sites. Total and ionic-only conductivities indicate that NFCO-x are a kind of mixed electronic-ionic conductors. Ionic transferring numbers are approximately 0.049 and 0.006 for NFCO-0.1 and NFCO-0.5, respectively, measured at 700?¡ãC in air. Co dopant in the NFCO-x improves the electronic conductivity at the expense of the ionic conductivity. For NFCO-0.5, electronic and ionic conductivities are approximately 0.24 and 9.6?¡Á?10^?4?S?cm^?1, respectively, measured also at 700?¡ãC in air. Unlike behaviour of the conductivities, the polarization resistance of symmetric cells with NFCO-x electrodes decreases when increasing the Co content (x) to a certain level, and then increases. The cell containing the NFCO-0.5 electrode exhibits the lowest polarization resistance (R_p), which is approximately 1.51?¦¸?cm² at 650?¡ãC. For single cells, the maximum power density is 320?mW?cm^?2 measured at 650?¡ãC using a 38-¦Ìm-thick SDC electrolyte and an NFCO-0.5 cathode.