To promote development of the unitized regenerative fuel cell, a new energy conversion-storage device, it is essential to look for a bifunctional catalyst with high efficiency and catalytic properties for oxygen evolution and reduction reactions. Herein, a novel PtRuIr electrocatalyst has been synthesized by a pulse electrodeposition method with selectively electrodepositing Ir on PtRu nanoclusters. The prepared catalysts were characterized by electrochemical analysis, scanning electron microscopy and energy dispersive spectrometer. The experimental results show that the PtRuIr catalyst with 10 mol% of Ir exhibits significantiy higher oxygen evolution and reduction currents compared to the PtRu and the PtRuIr catalysts with other contents of Ir, which is also supported by the electrochemical impedance data. In addition, a single water electrolysis cell and a H-2/O(2)fuel cell were performed simultaneously to evaluate the oxygen evolution and reduction performances, respectively, of the novel catalyst. The optimized catalyst with 90 mol% PtRu and 10mol% Ir shows higher oxygen evolution reactivity current density and higher round-trip efficiency in the water electrolysis single cell, and in the meantime, it also exhibits higher oxygen reduction current density and higher power density in the fuel cell, compared to those of the PtRu catalyst.