Evaluation of Fe and Mn co-doped layered perovskite PrBaCo2/3Fe2/3Mn1/2O5+δ as a novel cathode for intermediate-temperature solid-oxide fuel cell

Abstract

A B-site cation-deficient double-perovskite oxide, PrBaCo2/3Fe2/3Mn1/2O5+δ (PBCFM2), was successfully synthesized by a sol-gel method and systematically investigated as an efficient cathode for IT-SOFC. The PBCFM2 exhibits good thermally stability and broad chemical compatibility at high temperature. Appropriate substitution of Mn and Fe for Co dramatically decreases the thermal expansion coefficient (TEC) from 21.5 × 10–6 K–1 for PrBaCo2O5+δ to 17.8 × 10–6 K–1 to PBCFM2 at a temperature range of 30–1000 °C. The temperature dependence of conductivity of the PBCFM2 was tested from 300 °C to 850 °C and then confirmed using the p-type small-polaron transport mode. The maximum conductivity value was 72 S cm–1 at 600 °C. When using 300 µm of Sm0.2Ce0.8O1.9 (SDC) as an electrolyte, the area specific resistance (ASR) and peak power density values were 0.028 Ω cm2 and 588 mV cm–2 at 800 °C, respectively. The activity and performance of the PBCFM2 cathode are further improved by impregnation with nano-sized SDC particles. The composite cathode with two times impregnation provided the optimal nano-scale SDC loading and microstructure where the ASR and peak power densities were 0.023 Ω cm2 and 621 mV cm–2 at 800 °C, respectively. Our preliminary results lead us to propose that PBCFM and its composite cathodes are good candidate cathodes for IT-SOFC.