Mn1.5Co1.5O4−δ infiltrated yttria stabilized zirconia composite cathodes for intermediate-temperature solid oxide fuel cells

• The Mn1.5Co1.5O4 impregnated YSZ composites show cathode polarization resistances of 0.43 Ω cm2 at 800 °C.
• Co-impregnation of Mn1.5Co1.5O4–Sm0.2Ce0.8O2−δ can reduce the cathode polarization resistances to 0.15 Ω cm2 at 800 °C.
• Oxygen reduction kinetics is dominated by double ionization of adsorbed oxygen atoms or charge transfer reactions.

The composite cathodes of yttria stabilized zirconia (YSZ) and Mn1.5Co1.5O4 (MCO) are prepared by infiltration of the MCO oxides into porous YSZ backbones using aqueous solutions of the corresponding nitrate salts. Calcinations at 850 °C promote the formation of the MCO spinel oxide and yield nano-scale catalyst coatings on the YSZ pore walls. Impedance measurements on the symmetric MCO–YSZ cathode fuel cells show that the lowest polarization resistance in air at 800 °C is 0.43 Ω cm2 for the MCO impregnated YSZ composite at the MCO volume loading of 13.5%. Analysis of the impedance spectra suggest that the oxygen reduction kinetics is probably limited by double ionization of the adsorbed oxygen atoms or charge transfer at the triple-phase boundaries. Furthermore, introducing the oxide ion conductor of samarium-doped ceria as a second component in the coated catalysts yields much lower polarization resistances, e.g., 0.15 Ω cm2 at 800 °C.