Carbon nanotubes (CNTs) supported PtPd hollow nanospheres have been prepared by a replacement reaction between sacrificial cobalt nanoparticles and PtC62-, Pd2+ ions. The morphology, elemental composition, structure and electrocatalytic properties of the PtPd hollow nanospheres have been investigated by transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and typical electrochemical methods, respectively. The results indicate that the CNTs supported PtPd hollow nanospheres have excellent electrochemical properties for the electrooxidation of formic acid (high electrocatalytic activity and excellent stability) due to the high surface area resulted from the hollow nanosphere structure with porous shell. (c) 2008 Elsevier B.V. All rights reserved.