Electrochemical characteristics of nano-structured PrBaCo2O5+x cathodes fabricated with ion impregnation process

Nano-structured electro-catalyst of layered-structure cobaltite PrBaCo2O5+x (PBC) has been developed as cathode for solid oxide fuel cells (SOFCs) and excellent electrochemical activity towards oxygen reduction has been achieved. PBC nano-particles are deposited into porous samaria-doped ceria (SDC) backbones with an impregnation method. The fabrication processing parameters including composition of precursor solution, PBC loading, and firing temperature have been investigated to optimize the cathode microstructure and further to minimize the cathode interfacial polarization resistance, leading to a cathode interfacial polarization resistance of only 0.082 Ω cm2 at 600 °C, much lower than those reported for pure PBC electrode (0.86 Ω cm2), PBC–SDC composite cathode (0.25 Ω cm2) or various other impregnated cobaltite cathodes such as Sm0.5Sr0.5CoO3−δ (0.25 Ω cm2), La0.5Sr0.5CoO3−δ (0.31 Ω cm2), and La0.6Sr0.4Co0.2Fe0.8O3−δ (0.24 Ω cm2). The novel nano-structured PBC electrochemical reaction mechanism has found to be similar to that of a conventional PBC cathode. However, both oxygen ion incorporation and charge transfer steps are greatly accelerated for the novel nano-structured PBC cathode, suggesting that the impregnation process is very effective in fabricating layered-structure cobaltite electro-catalyst for intermediate-temperature SOFC cathode with enhanced electrode performance.

► Microstructure of the PBC impregnated cathode has been optimized. ► The impregnated PBC cathode has achieved an ASR as low as 0.08 Ω cm2 at 600 °C. ► Impregnated PBC shows similar reaction mechanism to that of a pure PBC cathode. ► Power density of 600 mW cm−2 at 600 °C is gained for cells with impregnated PBC.