Proton-conducting solid oxide fuel cells (SOFCs), consisting of BaCe0.7In0.3O3-delta (BCI30)-NiO anode substrates, BCI30 anode functional layers, BCI30 electrolyte membranes and BCI30-LaSr3Co1.5Fe1.5O10-delta (LSCF) composite cathode layers. were successfully fabricated at 1150 C. 1250 C and 1350 C respectively by a single step co-firing process. The fuel cells were tested with humidified hydrogen (similar to 3%H2O) as the fuel and static air as the oxidant. The single cell co-fired at 1250 C showed the highest cell performance. The impedance Studies revealed that the co-firing temperature affected the interfacial polarization resistance of a single cell as well as its overall electrolyte resistance. (C) 2009 Elsevier B.V. All rights reserved.