Pt/C electrocatalysts were modified by ceria with sol-gel and dipping process. The transmission electron microscopy (TEM) and cyclic voltammetry results show that some Pt active surfaces were covered by ceria, the electrochemical surface area of modified Pt/C is less than the unmodified one, and sol-gel process covers less electrocatalyst surface area than dipping process. The single fuel cell results reveal that the fuel cell using modified Pt/C as cathode electrocatalyst has an enhanced performance. In our opinion, this is because ceria was first reduced in cathode by electrochemical reaction, and then was oxidized by a middle product of oxygen reduction reaction, i.e., hydrogen peroxide, to its original state. Those processes promoted the reduced rate of oxygen and enhanced the performance of the fuel cell. (c) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.