▎ 摘　　要

The production of effective loading and direct deposition of Pt nanoparticles on graphene is difficult because this intriguing carbon material has highly hydrophobic surface properties. In this work, Pt/graphene sheet (GS) composites were successfully synthesized via a simple, effective, and environmentally benign one-pot supercritical carbon dioxide deposition route using dimethyl (1,5-cyclooctadiene) platinum(II) (PtMe2COD) as a soluble organometallic precursor. The preparation process obviates the need for solvents, which are often volatile and toxic. No post-treatment processes such as washing and drying are needed. Transmission electron microscopy shows that ultrafine metal nanoparticles with an average size as small as similar to 2 nm are densely and evenly decorated on the hydrophobic surfaces of. GS at Pt loadings up to 80 wt %. Electrochemical studies reveal that the prepared Pt/GS composites possess notably higher catalytic activity and better stability toward methanol electrooxidation in comparison with Pt/multiwalled carbon nanotube and Pt/carbon black composites. The supercritical carbon dioxide deposition method could be easily extended to the fabrication of other graphene-based metal composites with desirable properties by selecting suitable organometallic precursors.