Sm0.5Sr0.5CoO3-delta (SSC) infiltrated Ce0.9Gd0.1O2-delta (GDC) composite cathodes are developed for protonic ceramic fuel cells (PCFCs). Although the SSC infiltrated GDC cathodes make little contribute to expending the reaction sites of water formation, it can significantly improve the oxygen reduction dynamics among the whole electrochemical reaction. The symmetric half cell and single cell testing results demonstrate the high electrochemical activity of SSC infiltrated GDC cathodes. Moreover, the single cell is stable at 600 degrees C for 120 h in humidified H-2 and humidified H-2-CO. The encouraging results indicate that the SSC infiltrated GDC could be the promising composite cathodes for application in PCFCs. (C) 2016 Elsevier B.V. All rights reserved.