For the fabrication of high-efficient bifunctional electrocatalyst of oxygen electrode, several electrocatalysts were prepared and tested on the URFC performance including both fuel cell and water electrolysis in a single cell URFC system. The catalysts revealed fuel cell performance in the order of Pt black > PtIr > PtRuOx > PtRu similar to PtRuIr > PtIrOx and water electrolysis performance in the order of PtIr similar to PtIrOx > PtRu > PtRuIr > PtRuOx similar to Pt black. Considering both results PtIr showed the best URFC performance. With increasing Ir or IrOx composition from 0 to 50 wt% in PtIr and PtIrOx catalysts the fuel cell performance decreased while the water electrolysis performance significantly improved. Hence, the PtIr catalyst including I wt% Ir revealed the highest URFC efficiency. The catalyst content for the URFC system was optimized as 1.0 mg/cm(2) of Pt black as hydrogen electrode and 2.0 mg/cm(2) of PtIr (99:1) as oxygen electrode. (c) 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.