Synthesis of platinum/graphene composites by a polyol method: The role of graphite oxide precursor surface chemistry

Graphite oxide (GO) with varied oxidation degrees and hexachloroplatinic acid were used as precursors for the synthesis of Pt/graphene composites via a polyol approach. It is revealed that the epoxy-rich basal planes of GO serve as the active sites for the nucleation of Pt nanoparticles via COPt bonds. With the increased oxidation degree of GO, both the nucleation sites and the repulsive forces between the GO and hexachloroplatinic anions and between the graphene and the negatively charged Pt nanoparticles increase, and this kind of subtle balance leads to a first decrease and then an increase of Pt size and size distribution on the graphene as well as the decrease of Pt loading. Moreover, adjusting the pH in the aging stage significantly increases the Pt loading both on the basal planes and at the edges of graphene, which is attributed to the introduction of positively charged sites by π sites on the basal planes of graphene and the protonation of carbonyl and carboxyl groups at the edges.