Evaluation of strontium-site-deficient Sr<sub>2sub>Fe<sub>1.4sub>Co<sub>0.1sub>Mo<sub>0.5sub>O<sub>6-δsub>-based perovskite oxides as intermediate temperature solid oxide fuel cell cathodes

<p>In this paper strontium-site-deficient Sr<sub>2sub>Fe<sub>1.4sub>Co<sub>0.1sub>Mo<sub>0.5sub>O<sub>6-δsub>-based perovskite oxides (S<sub>xsub>FCM) were prepared and evaluated as the cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). All samples exhibited a cubic phase structure and the lattice shrinked with increasing the Sr-deficiency as shown in XRD patterns. XPS results determined that the transition elements (Co/Fe/Mo) in S<sub>xsub>FCM oxides were in a mixed valence state, demonstrating the small polaron hopping conductivity mechanism existed. Among the samples, S<sub>1.950sub>FCM presented the lowest coefficient of thermal expansion of 15.62 × 10<sup>-6sup> K<sup>-1sup>, the highest conductivity value of 28 S cm<sup>-1sup> at 500 °C, and the lowest interfacial polarization resistance of 0.093 Ω cm<sup>2sup> at 800 °C, respectively. Furthermore, an anode-supported single cell with a S<sub>1.950sub>FCM cathode was prepared, demonstrating a maximum power density of 1.16 W cm<sup>-2sup> at 800 °C by using wet H<sub>2sub> (3% H<sub>2sub>O) as the fuel and ambient air as the oxidant. These results indicate that the introduction of Sr-deficiency can dramatically improve the electrochemical performance of Sr<sub>2sub>Fe<sub>1.4sub>Co<sub>0.1sub>Mo<sub>0.5sub>O<sub>6-δsub>, showing great promise as a novel cathode candidate material for IT-SOFCs.p>

High performance cobalt-free Cu<sub>1.4sub>Mn<sub>1.6sub>O<sub>4sub> spinel oxide as an intermediate temperature solid oxide fuel cell cathode

<p>In this work Cu<sub>1.4sub>Mn<sub>1.6sub>O<sub>4sub> (CMO) spinel oxide is prepared and evaluated as a novel cobalt-free cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs). Single phase CMO powder with cubic structure is identified using XRD. XPS results confirm that mixed Cu<sup>+sup>/Cu<sup>2+sup> and Mn<sup>3+sup>/Mn<sup>4+sup> couples exist in the CMO sample, and a maximum conductivity of 78 S cm<sup>−1sup> is achieved at 800 °C. Meanwhile, CMO oxide shows good thermal and chemical compatibility with a 10 mol% Sc<sub>2sub>O<sub>3sub> stabilized ZrO<sub>2sub> (ScSZ) electrolyte material. Impedance spectroscopy measurements reveals that CMO exhibits a low polarization resistance of 0.143 Ω cm<sup>2sup> at 800 °C. Furthermore, a Ni-ScSZ/ScSZ/CMO single cell demonstrates a maximum power density of 1076 mW cm<sup>−2sup> at 800 °C under H<sub>2sub> (3% H<sub>2sub>O) as the fuel and ambient air as the oxidant. These results indicate that Cu<sub>1.4sub>Mn<sub>1.6sub>O<sub>4sub> is a superior and promising cathode material for IT-SOFCs.p>