In this paper, we investigated the effect of ozone oxidation on properties of commercial carbon black supported platinum (Pt) nanoparticles for the methanol electro-oxidation reaction. The results indicated that the oxygenated functional groups could be introduced on the carbon black evenly with the increase of processing time. Apparently, mainly introduced oxygenated functional group is carboxyl. Platinum nanoparticles could be uniformly immobilized on the surfaces of carbon black treated with ozone, which has significant high electro-catalytic activity and stability for methanol electrooxidation. This phenomenon is attributed to the fact that oxygen-containing groups (mainly for carboxyl functional groups) produced by ozone oxidation are good for improving the dispersion and strengthening the interaction between support and platinum nanoparticles. The ozone oxidation conditions had significant effects on the defects properties of carbon black which showed a positive correlation between the defect levels and methanol electro-oxidation performances. This paper also fully demonstrated the positive relationship between carboxyl functional groups and the performance of methanol electrocatalytic oxidation. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.