A carbon nanostructure has fabricated from covalently grafted platinum (Pt) to multi walled carbon nanotube (MWCNT) with the assistance of sulfur atom on the MWCNT's sidewall, MWCNT-S-Pt. The MWCNT-S-Pt displays an excellent electrocatalytic performance for oxygen-reduction reaction (ORR) than that of an unbonded Pt to MWCNT, MWCNT/Pt. Here we describe a comparative study of the ORR on two MWCNT-supported Pt-based catalysts in aqueous acidic electrolyte. Both MWCNT-S-Pt and MWCNT/Pt catalysts have the compositions of 1.03 and 2.18 at% Pt, respectively. For the characterization, the bonding features have confirmed by the X-ray photoelectron spectroscopic (XPS) and electron microscopy have used to determine the size and shape as well as the distribution of the particle on both catalysts. Electrochemical measurements have performed using the cyclic voltammetry and hydrodynamic voltammetry methods in 0.1 mol l(-1) HCIO4 solution. Kinetic analysis in comparison to unbonded MWCNT/Pt a significant enhancement for the covalently bonded MWCNT-S-Pt has been found. The MWCNT/Pt is unstable at electrode potentials for long term use than that of MWCNT-S-Pt. Ring-current collection measurements for peroxide indicate MWCNT-S-Pt catalyst has a less peroxide yield. (C) 2012 Elsevier Ltd. All rights reserved.