Like the other newly discovered carbon nanomaterials, such as fullerenes and carbon nanotubes, graphene, a monolayer graphite, and its composites have been widely applied to the field of electrocatalysis due to that graphene have unique structures and inherent properties including high specific surface areas, chemical and electrochemical inertness, easy surface modification, higher electron mobility and broad electrochemical windows. Thus, the use of graphene as substrates of catalysts provides a new opportunity for designing and constructing next-generation catalysts. Especially, graphene decorated with metallic nanoparticles can be employed as fuel cell electrocatalysts, in which they plays an important role in improving the charge-transfer efficiency and decreasing the overpotential of electrochemical reactions such as methanol oxidation and oxygen reduction.

However, there are still unresolved issues in practical use, such as durability. In situ growth method is the most widely used method for preparing graphene/metallic nanoparticle composites. Hydrophobic and/or electrostatic interactions are the main driving forces of adsorbing metallic nanoparticles on graphene surfaces. These relatively week binding interaction often gave rise to desorption of the nanoparticles from the graphene surface during charging and discharging operation at high temperature.

Very recently, we reported a fabrication of Pt catalysts supported on carbon nanoballs, as well as characterization of their electrochemical activities (Saito et al.,

J. Vac. Sci. Technol. A, 27(4) pp.826-830). Plausible mechanism has remained a mystery, Pt catalysts were strongly attached to the carbon nanoball surface. The resultant products showed relatively higher durability compared with than that of catalysts prepared by conventionally used approaches. In this work, we demonstrate surface decoration of chemically converted graphene with various metallic nanoparticles by the originally-developed solution plasma processing. Structural characterization and electrochemical activities of the all product was performed by a combination with TEM, XRD, AFM, Raman spectroscopy, and measurements of oxidation-reduction potential [file:///C:/Users/%E5%AE%9A%E6%9C%AB%E4%BD%B3%E7%A5%90/AppData/Roaming/EdMax/Attachment/20110504_133844_dtub14/AVS%20%E3%82%A2%E3%83%96%E3%82%B9%E3%83%88%EF%BC%88%E5%AE%9A%E6%9C%AB%EF%BC%89_revised_zettsu0504.docx] .