We have proposed a novel deposition method of thin Pt catalysts onto Nation membranes impregnated with polypyrrole (PPy) for unitized regenerative fuel cells (URFCs). We demonstrated that the polypyrrole impregnated into Nafion membrane not only offered electronic conduction pathways necessary to sink electrons generated from the chemical reduction of platinic chloride, but also enhanced the direct loading of Pt particles onto the Nation surface. The distribution and thickness of Pt particles deposited on the PPy/Nafion composite membrane was observed by energy dispersive X-ray spectrometry. Atomic force microscopy and scanning electron microscopy were implemented to investigate the morphology of PPy/Nafion composite membrane surface and the influence of Pt loading onto the Pt/PPy/Nafion electrode surface morphology, respectively. The performance of fuel cell and water electrolysis was discussed in the reference to an I-V curve. (C) 2004 Elsevier B.V. All rights reserved.