Effect of Fe doping on the oxygen reduction reaction activity of a PrNi0.5Co0.5O3−δ cathode for protonic ceramic fuel cells

Abstract

Protonic ceramic fuel cells (PCFCs) have demonstrated great potential as the most promising electrochemical energy conversion devices with high efficiency at intermediate temperatures (500–700 °C). One of the major challenges for their widespread application is the slow oxygen reduction reaction (ORR) kinetics and poor durability of cathodes. This work reports an optimized Fe-doped perovskite with a nominal composition of PrNi_0.5Co_0.3Fe_0.2O_3−δ. It is shown that Fe substitution can change the crystal structure and affect the ORR performance. The expanded crystal lattice induced by Fe doping may favor the formation and movement of charge carriers in perovskite oxides. Furthermore, the incorporation of Fe leads to more reactive oxygen species (O₂²⁻/O⁻), while facilitating the oxygen dissociation process as well as the surface exchange and ion diffusion process. The optimized cathode shows enhanced electrochemical activity with a significantly reduced area-specific resistance of 0.129 Ω cm² and improved durability with no obvious degradation at 650 °C. When applied as a cathode in single cells, a peak power density of 1.23 W cm⁻² while maintaining a relatively stable performance (at 0.5 A cm⁻²) is delivered at 650 °C.