Protonic ceramic fuel cells offer the potential for environmentally sustainable and cost-effective electric power generation. However, the power outputs of protonic ceramic fuel cells are far from the requirements due to the lack of active cathodes. In this work, porous thin sheets CaxY1-xFe0.5Co0.5O3-delta = 0.1, 0.3 and 0.5) are synthesized by a modified pechini method and investigated as cathode materials for protonic ceramic fuel cells. CaxY1-xFe0.5Co0.5O3-delta show high electrical conductivities and excellent chemical compatibility with Ba (Zr0.1Ce0.7Y0.2)O-3 electrolyte. The maximum electrical conductivity of Ca0.3Y0.7Fe0.5Co0.5O3-delta reaches 202 S cm(-1) in air at 750 degrees C. The detailed mechanism for oxygen reduction reaction reveals that the rate -limiting step of oxygen reduction reaction is transformed from charge transfer to O-2 adsorption -dissociation with temperature rising or Ca doping. The composite cathode Ca0.3Y0.7Fe0.5Co0.5O3-delta-Ba(Zr0.1Ce0.7Y0.2)O-3 presents a relatively low polarization resistance of 0.07 Omega cm(2) at 750 degrees C in air. The power density of the anode -supported cell of NiO- Ba(Zr0.1Ce0.7Y0.2)O-3 vertical bar Ba(Zr0.1Ce0.7Y0.2)O-3 vertical bar Ca0.3Y0.7Fe0.5Co0.5O3-delta-Ba(Zr0.1Ce0.7Y0.2)O-3 is 798 mW cm(-2) as the electrolyte thickness is about 150 mu m. The prepared CaxY1-xFe0.5Co0.5O3-delta oxides are promising candidates as high-performance cathodes for protonic ceramic fuel cells.