To improve their electrochemical stability as catalyst supports for proton exchange membrane (PEM) fuel cells, carbon nanotubes (CNTs) are heat treated in an ammonia atmosphere. High-resolution transmission electron microscopy, nitrogen adsorption, Raman spectroscopy, and X-ray photoelectron spectroscopy are employed to study the temperature effect on the structure of the heat-treated CNTs (H-CNTs), and a thorough investigation of their resistance to electrochemical oxidation is also measured by an electrochemical technique. The amount of surface oxides on the CNTs is visibly high in comparison to the H-CNTs after 48 h of oxidation, indicating that the H-CNTs have a higher resistance to electrochemical oxidation. Pt nanoparticles supported on both CNTs and H-CNTs are fabricated through a polyol process in an ethylene glycol solution. The improvement of the dispersion of Pt nanoparticles on nanotubes from the heat treatment is demonstrated, and the results show that the Pt nanoparticles deposited on the H-CNTs heated at 1000 degrees C are electrochemically accessible. Therefore, they can be used as a durable support for Pt catalysts in fuel cells. (C) 2011 Elsevier Ltd. All rights reserved.