Electrochemical characteristics of nano-structured PrBaCo 2O 5+ x cathodes fabricated with ion impregnation process

Abstract

Nano-structured electro-catalyst of layered-structure cobaltite PrBaCo 2O 5+ 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 cm 2 at 600 °C, much lower than those reported for pure PBC electrode (0.86 Ω cm 2), PBC–SDC composite cathode (0.25 Ω cm 2) or various other impregnated cobaltite cathodes such as Sm 0.5Sr 0.5CoO 3− δ (0.25 Ω cm 2), La 0.5Sr 0.5CoO 3− δ (0.31 Ω cm 2), and La 0.6Sr 0.4Co 0.2Fe 0.8O 3− δ (0.24 Ω cm 2). 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.