Carbon supported Pt nanoparticles are widely used as electrocatalysts for important applications. In the current paper, we report catalysts of platinum nanoparticles loaded on multi-walled carbon nanotubes (Pt/MWCNTs) prepared via a potentiostatic electrodeposition method in the solution bath without supporting electrolyte. It has found that the as-prepared catalyst of Pt/MWCNTs exhibits higher activity and stability than the commercial Pt/C catalyst does toward ethanol electrooxidation. From analysis of SEM and HRTEM, the average size of Pt particles is ca. 4 nm and the loading of Pt in the Pt/MWCNTs catalyst is about 20 wt.%. Surface step atoms which serve as active sites in electrooxidation reactions were observed on individual Pt particle on both Pt/MWCNTs and commercial Pt/C catalysts by using HRTEM. However, a higher density of step atoms on Pt/MWCNTs than that on Pt/C has been indicated by COad stripping experiments, which is attributed to the origin of the higher catalytic activity of the Pt/MWCNTs in comparison with commercial Pt/C catalyst with the same Pt loading. It has also demonstrated that the developed electrochemical method is a promising and efficient way to synthesize carbon supported Pt catalysts. (C) 2013 Elsevier Ltd. All rights reserved.