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

A B-site cation-deficient double-perovskite oxide, PrBaCo2/3Fe2/3Mn1/2O5+delta (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 x 10(-6) K-1 for PrBaCo2O5+delta to 17.8 x 10(-6) K-1 to PBCFM2 at a temperature range of 30-1000 degrees C. The temperature dependence of conductivity of the PBCFM2 was tested from 300 degrees C to 850 degrees C and then confirmed using the p-type small-polaron transport mode. The maximum conductivity value was 72 S cm(-1) at 600 degrees C. When using 300 mu m of Sm0.2Ce0.8O1.9 (SDC) as an electrolyte, the area specific resistance (ASR) and peak power density values were 0.028 Omega cm(2) and 588 mV cm(-2) at 800 degrees 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 Omega cm(2) and 621 mV cm(-2) at 800 degrees C, respectively. Our preliminary results lead us to propose that PBCFM and its composite cathodes are good candidate cathodes for IT-SOFC.