Vulcan XC72R carbons were pretreated using a modified Hummers method and adopted as the support of palladium nanoparticles for formic acid electrooxidation. XPS analysis was used to investigate the surface species of the pretreated XC72R (XC72R-O), indicating a significant increase in the content of surface carboxyl groups. The structural properties of Pd nanoparticles deposited on the XC72R-O (Pd/XC72R-O) were determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and their electrochemical performance was evaluated by cyclic voltammetry (CV) and chronoamperometry. Pd nanoparticles in the Pd/XC72R-O display an average size of similar to 6.7 nm with narrow size distribution. Electrochemical studies for formic acid oxidation reveal that the Pd/XC72R-O presents much higher electrocatalytic activity than that of the Pd/XC72R and commercial Pd/C, which may be due to the formation of carboxyl groups enhanced the interaction between the Pd particles and the carbon support, facilitating the dispersion of Pd particles and the formation of preferred plane orientation available for electrocatalytic reaction. (C) 2013 Elsevier B.V. All rights reserved.