The electrochemical deposition of Pt-Ru nanoparticles on carbon nanotubes (CNTs) supports and their electro-catalytic activities, were investicrated. Pt-Ru catalysts of 4-12 run average size were grown successfully on supports by step-potential plating methods. Electro-plating at 0.06 s step intervals was sufficient to obtain small-size 4.8 nm particles, showing good electrochemical activity. The catalysts' loading contents were enhanced by increasing the plating time. The sizes and morphological structures of the Pt-Ru/support catalysts were evaluated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electrochemical behaviors of the Pt-Ru/support catalysts for methanol oxidation were investigated according to their characteristic current-voltage curves in a methanol solution. In the result, the electrochemical activity increased with increased plating time, reaching the maximum at 24 min, and then decreased. The improved catalytic activity was correlated to the small particle size and the higher specific surface area of the catalysts. (c) 2007 Elsevier Ltd. All rights reserved.