Sm0.5Sr0.5CoO3-delta-Ce0.8Sm0.2O2-delta (SSC-SDC) composites, which are often used as the cathodes for solid oxide fuel cells (SOFCs) with oxygen-ion conducting electrolytes, have been recently shown to be also applicable in SOFCs based on proton conductors such as BaZr0.1Ce0.7Y0.2O3-delta (BZCY). The electrochemical performances of blank SSC-SDC electrodes on BZCY electrolytes are substantially improved in this work by impregnating SSC nanoparticles additionally. When the loading increases, the interfacial polarization resistance of the symmetric cell decreases gradually at first, notably when it exceeds 14 wt.%, and to the lowest value at about 22 wt.%. Furthermore, impregnating SSC reduces the low-frequency-arc resistance that corresponds to the surface exchange step. In addition, impregnating SSC reduces the activation energy for oxygen reduction from 1.14 to 0.70 eV, thus resulting in significantly improvement on electrode performance at the reduced temperatures for SOFCs based on proton conductors. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.