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 Omega cm(2) at 600 degrees C, much lower than those reported for pure PBC electrode (0.86 Omega cm(2)), PBC-SDC composite cathode (0.25 Omega cm(2)) or various other impregnated cobaltite cathodes such as Sm0.5Sr0.5CoO3-delta (0.25 Omega cm(2)), La0.5Sr0.5CoO3-delta (0.31 Omega cm(2)), and La0.6Sr0.4Co0.2Fe0.8O3-delta (0.24 Omega 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. (C) 2011 Elsevier B.V. All rights reserved.