Doped PrMn0₃Perovskite Oxide as a New Cathode of Solid Oxide Fuel Cells for Low Temperature Operation

Cathodic overpotentials of Ln_0.6Sr_0.4Mn0₃(Ln = La, Pr, Nd, Sm, Gd, Yb, and Y) were studied for a new cathode of solid oxide fuel cell (SOFC). Cathodic overpotentials as well as the electrical conductivity strongly depended on the rare earth cations used for the A sites of perovskite oxide. Strontium doped PrMnO₃exhibited the highest electrical conductivity among the examined perovskite oxide containing Mn for B sites. Moreover, overpotentials of Sr-doped PrMnO₃cathode maintained low values in spite of decreasing the operating temperature. Consequently, almost the same power density of SOFC with La_0.6Sr₀.₄Mn0₃cathode can be obtained at about 100 K lower operating temperature by using Sr-doped PrMnO₃as the cathode. The overpotentials and electrical conductivity decreased and increased with increasing the amount of Sr dopant in PrMnO₃, respectively, and the lowest overpotential was attained at x = 0.4 in Pr_1-xSr_xMnO₃. Comparing with La_0.6Sr_0.4MnO₃oxide, the reactivity of Pr_0.6Sr_0.4MnO₃with Y₂O₃-stabilized ZrO₂is much less than that of La₀.₆Sr₀.₄MnO₃ and furthermore, the matching of thermal expansion of Pr_0.6Sr_0.4MnO₃with Y₂O₃-ZrO₂was satisfactorily high. Therefore, perovskite oxide of Pr₀.₆Sr_0.4MnO₃has a great possibility of the cathode materials for decreasing the operating temperature of solid oxide fuel cells.