▎ 摘　　要

Graphite oxide nanosheets with three different sheet sizes were prepared from different graphite materials. The graphite oxide nanosheets were used as precursors to prepare three 20 mass % Pt/graphene composite electro-catalysts composed of different sizes of graphene. The structure and electrochemical properties in 0.1 M HClO4 at 60 degrees C of the three Pt/graphene electrocatalysts were studied. Well dispersed Pt nanoparticles with 2.2 nm average diameter and electrochemically active surface area of similar to 50 m(2) (g-Pt)(-1) were obtained irrespective of the size of graphene. Despite the similarity in Pt nanoparticle state, the oxygen reduction reaction was strongly affected by the size of graphene. Smaller sized graphene afforded higher mass and specific activity towards the oxygen reduction reaction.