Novel methanol-tolerant catalysts for oxygen reduction reaction (ORR), IrxCo1-x/C (x = 0.3-1.0), were synthesized by a conventional impregnation method. These carbon-supported catalysts showed particle sizes of 2.7-5.0 nm. The catalyst activity and the catalyzed ORR kinetics were characterized by cyclic voltammetry and rotating disk electrode methods. Among these Ir Co-x(1-x)/C catalysts, the alloy with a formula of IrxCo1-x/C with x value in the range of 0.7-0.8 exhibited the highest mass and specific activities. Compared to a Pt/C catalyst, these alloy catalysts have much stronger methanol tolerance in terms of ORR onset potential (or open-circuit potential). Based on the rotating disk electrode measurements, it was confirmed that these IrxCo1-x/C alloy catalysts could catalyze a complete four-electron transfer reaction of oxygen to water. These results strongly suggest that the novel Ir-Co metal alloy catalysts synthesized in this work could be promising for DMFC cathodes. (c) 2007 Elsevier B.V. All rights reserved.