Decoration, Migration, and Aggregation of Palladium Nanoparticles on Graphene Sheets

As a two-dimensional carbon nanomaterial, graphene has a high surface area and good chemical stability; therefore, its potential applicability in composite materials and as a catalyst support is high. Here, we report a facile process to decorate graphene sheets with well-dispersed Pd nanoparticles. By the in situ formation and adhesion of Pd nanoparticles to the thermally exfoliated graphene (TEG) sheets suspended in a solvent, a Pd/TEG composite was prepared and characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller (BET) surface area analysis. The migration and aggregation of Pd nanoparticles on the graphene sheets was directly observed by scanning transmission electron microscopy. As the composite was heated to 700 degrees C, there was little movement of the Pd nanoparticles; on heating to 800 degrees C, well below the melting temperature, the Pd nanoparticles began to migrate, coalesce, and agglomerate to form larger particles. The aggregation behavior was further confirmed by X-ray diffraction analysis of the Pd/TEG composite before and after being annealed at 800 degrees C. The graphene sheets provided a real-time imaging platform with nanometer-scale thickness to study the thermal stability and migratory behavior of nanoscale materials.