Oxygen Reduction Reaction Mechanism on PrSrCo2-x Fe x O5+d (x=0, 1, 2) and Sm0.2Ce0.8O1.9 Composite Cathodes for Intermediate-Temperature Solid Oxide Fuel Cells

Perovskite-type mixed ionic and electronic conductors are finding applications in intermediate-temperature solid oxide fuel cells. Here, we study the effects of substituting Co with Fe on the crystal structure and electrical and electrochemical properties of PrSrCo2-xFexO5+d (PSCF, x = 0, 1, 2). The electrochemical performance of symmetrical half-cells of PrSrCo2-xFexO5+d and Sm0.2Ce0.8O1.9 composite cathodes with the Sm0.2Ce0.8O1.9 electrolyte was measured using electrochemical impedance spectroscopy at 600-750 degrees C. The oxygen reduction reaction (ORR) mechanism was analyzed as a function of temperature and oxygen partial pressure (pO(2)) using the distribution function of relaxation times (DFRT). The electrical conductivity measurements of the PSCF pellets were in the range of 100-1300 S cm(-1). The PSCF (x = 1) - Sm0.2Ce0.8O1.9 composite cathode yielded the lowest area specific resistance (ASR) value of 0.07 Omega cm(2) at 750 degrees C for ORR. DFRT and pO(2) studies showed that impedance arcs corresponding to the high frequency could be attributed to the oxygen ion transfer resistance while the medium-low frequency impedance arcs could be correlated with the charge transfer resistance at the cathode/gas interface followed by ion incorporation. This study demonstrates that the partial substitution of Fe on the Co site improves the ORR activity of PSCF perovskites.

Automated summary

This study investigates the effects of substituting Co with Fe on the crystal structure and electrochemical properties of the Perovskite-type mixed ionic and electronic conductors. The results show that partial substitution of Fe on the Co site improves the oxygen reduction reaction (ORR) activity of the PSCF perovskites.