Pt-free fuel cells were investigated using a proton-conducting Sn0.9In0.1P2O7 electrolyte at intermediate temperatures between 150 and 300 degrees C. Transition metal oxides were applied as non Pt cathode catalysts. A ZrO2/C catalyst showed the highest catalytic activity for the oxygen reduction reaction among the metal oxides tested. The catalytic activity of ZrO2/C was further improved by optimizing the heat-treatment temperature for ZrO2/C. XRD measurements revealed that the high catalytic activity was attributed to the crystal structure of tetragonal ZrO2. Finally, we evaluated performance of a Pt-free fuel cell using the ZrO2/C cathode with a Mo2C-ZrO2/C anode that shows Pt-like behavior in reducing atmospheres. Reasonable performance was achieved by operating the Pt-free fuel cell at intermediate temperatures above 200 degrees C. (C) 2008 Elsevier B.V. All rights reserved.