The cobalt oxyphosphides supported on carbon black were prepared using incipient wetness method and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The possibility of their application as the electrocatalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cell (PEMFC) was investigated and the electrocatalytic activities were evaluated by the electrochemical measurements and single cell test, respectively. The electrocatalyst presents attractive catalytic activity towards ORR and good stability in acid media and exhibits an onset potential for oxygen reduction as high as 0.69 V (RHE) in H(2)SO(4) solution. The maximum power density obtained in a H(2)/O(2) PEMFC is 57 mW cm(-2) with Co(4)P(2)O(9)/C loading of 1.13 mg cm(-2). No significant performance degradation is observed over 50 h of continuous fuel cell operation. The combination of heteroatom P with nanostructured oxides with high stability, excellent functionality and low cost which are prerequisites for large-scale applications, probably provide a new solution for the critical challenge of finding effective cathode materials for PEMFC. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.