Iridium oxide supported on Vulcan XC-72 carbon black (IrO(2)/C) as a cathode catalyst for polymer electrolyte fuel cell (PEFC) has been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurement. The IrO(2) particles were 8-160 rim in diameter. The oxygen electroreduction activity was studied by cyclic voltammetry (CV). It was found that IrO(2)/C had high oxygen reduction reaction (ORR) activity. The performance of the membrane electrode assemble (MEA) was also tested in a single PEFC and showed that IrO(2)/C catalyst would be potential candidates for use as cathode catalyst in PEFC. (C) 2011 Elsevier B.V. All rights reserved.