Abstract
Carbon nanomaterials, including herringbone graphite carbon nanofibers (GNF <sub>H</sub> ), multiwalled carbon nanotubes (MWCNT), and carbon black, were surface-modified by a new poly(vinylpyrrolidone) (PVP) grafting process as well as by the conventional acid-oxidation (AO) process, and characterized by FTIR, TGA, Raman, HRTEM, XRD, and XPS measurements. Pt nanoparticles of 1.8 nm were evenly deposited on all PVP-grafted carbon nanomaterials. The effects of the two surface modification processes on the dispersion, average Pt nanoparticle sizes, the electrocatalytic performance, and electrical conductivities of Pt-carbon nanocomposites in direct methanol oxidation were systematically studied and compared. It was found that the PVP-grafted carbon nanomaterials have much less loss in the electric conductivity and thus better electrocatalytic performance, 17-463% higher, than their corresponding acid oxidation-treated nanocomposites. The electrocatalytic performance of the Pt-carbon nanocomposites decreases in the following order: Pt-PVP-GNF <sub>H</sub> > Pt-PVP-MWCNT <sub>arc</sub> > Pt-AO-MWCNT <sub>arc</sub> > Pt-PVP-MWCNT <sub>CVD</sub> > Pt-AO-MWCNT <sub>CVD</sub> > Pt-XC-72R > Pt-AO-GNF <sub>H</sub> , with the Pt-PVP-GNF <sub>H</sub> nanocomposite having ∼270% higher performance than that of the Pt-Vulcan XC-72R nanocomposite. In addition, PtRu-PVP-GNF <sub>H</sub> shows even better (50% higher) electrocatalytic activity than the Pt-PVP-GNF <sub>H</sub> nanocomposite at a 0.6 V applied voltage. © 2007 American Chemical Society.