Synthesis And Self-assembly Of Pt/Reduced Graphene Oxide Composites And Their Electrooxidation Towards Methanol Oxidation

Graphene is a two-dimensional atomic crystals, namely a single layer of carbon atoms joined together by sp2 covalent bonds, which shows unique electrical, optical, mechanical and magnetic properties due to its large surface area and high conductivity, so that graphene and its compounds have wide applications in the areas of sensing, energy, electronics, catalysis. Numerous reports demonstrate that graphene is a good alternative to replace traditional carbon as the substrate of Pt catalytst, which can efficiently improve the catalytic performance by weanken the posioning of CO-like intermidiates to platinum. Despite previous successes, it is still chanlleging for controllable fabrication of Pt nanoparticles on graphene surface. Based on that, in this thesis, controllable preparation of graphene/platinum composites(Pt/RGO) was achieved involving the control of Pt content and the arrangement of Pt nanoparticles on graphene suface. As-prepared Pt/graphene composites can be assembled into thin films. Pt/graphene composites and its thin films were assessed as electrocatalysts for methanol oxidation.1. Pt/reduced graphene oxide(Pt/RGO) composites was synthesized by reducing H2 Pt Cl6 with Na BH4 in graphene dispension. Pt contents of Pt/RGO can be controlled by adjusting the added amount of Pt precusors. With the increase of Pt precusor amount, Pt contents of Pt/RGO also increases. Regardless of the amount of Pt precusors, Pt species in all samples exists as Pt[111]-oriented single crystals close to 3 nm. Also, with the increase of Pt contents, the arrangement of Pt nanocrystals on graphene surface evolves from sparse individual state to closely-packed monolayer, to linear aggregates. T hree dimensional aggregates of Pt nanocrystals did not observed in all samples. This approach is simple and quick for efficiently achieving the control of Pt nanoparticles arrangement on graphene surface.2. Electrocatalytic performances of Pt/RGO composite catalysts towards methanol oxidation were assessed systematically. The results show that, with the increase of the loading amount of platinum, the specific activities and mass activities of Pt/RGO catalysts exhibit the same change: increase and then decrease. Pt24/RGO(Pt, 24 wt%) shows the best catalytic activity and stability among all samples due to the closely-packed structure of Pt nanocrystals, which is 3.26 times in the mass activity, 2 times in the specific activity, better than Pt/C.3. Pt24/RGO composites were assembled into a monolayer at toluene-water two phase interface for methanol elecrooxidatioin. T he results indicate that Pt24/RGO monolayer exhibits much better catalytic activity and stability than Pt24/RGO catalysts prepared above. The specific activity is 2.3 times better than the commercial Pt/C, which may attributed to the mechanic stabiltiy of Pt24/RGO monolayer.