Preparation And Function Of Graphene With Assistance Of Supercritical Carbon Dioxide And Their Application In Fuel Cells

Graphene, a one-atom layer of graphite, possesses a unique two-dimensional structure and excellent mechanical, thermal, and electrical properties. Since its discovery, graphene has attracted intensive research interest. Currently, great effort has been carried out for the preparation and function of graphene, as well as its use in the energy conversion filed, such as fuel cells.In this work, we proposed a novel method for the preparation and function of graphene by liquid-phase exfoliation with the aid of supercritical carbon dioxide, and then studied the resulting graphene’s application in the direct methanol fuel cells (DMFCs) as Pt catalyst supporting materials.Firstly, graphite was successfully exfoliated into graphene by pyrene and another three derivatives (1-pyrenecarboxylic acid (PCA),1-pyrenebutyric acid (PBA) and1-pyrenamine (PA)) with the assistance of supercritical carbon dioxide (SC CO2). The resulting graphene was characterized by transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), Raman spectra and Fluorescence spectra. High-quality and noncovalent functionalized single or few layer graphene were obtained. Van der Waals corrected first-principles approach within density functional theory (vdW-DFT2) was used to investigate the interaction energy of different pyrene-derivatives on graphene and inside the two graphene. The results showed that pyrene and pyrene-derivatives can act as a "molecular wedge" to exfoliate graphene from graphite well. Further graphene/gold nanoparticles composite was also successfully obtained, it indicates that pyrene-derivatives firmly adsorbed on the surface of graphene can be acted as the interlinkers between graphene and Au NPs or other rare metal nanoparticles. So the functionalized graphene with different pyrene-derivatives will have potential application in nano functional materials, nano reactor device and catalysis field.1-pyrenamine (PA) noncovalent functionalized graphene nanosheets are prepared through solvent-exfoliation expanded graphite with the same methods. Then, it is used as supporting materials for platinum to investigate the potential application of obtained nanocomposite in DMFCs. Transmission electron microscope (TEM) images reveal that Pt nanoparticles are evenly dispersed on the PA-modified graphite nanosheets (PA-GNS) with an average size of3.0nm. PA-GNS/Pt nanocomposites exhibit better electrocatalytic activity (1.4times) and stability (3.5times) toward methanol oxidation than commercial catalyst JM-C/Pt. The results suggest that noncovalent functionalization of GNS by PA can be used as highly efficient and stabile catalyst supports for the methanol electrooxidation in DMFCs.