Preparation Of Pristine Graphene Via Liquid Phase Exfoliation And Its Potential Applications In Metal Based Electrocatalysts Towards Methanol Oxidation And Reinforcing Additives For Polymer

Owing to its unique two-dimensional structure, excellent electrical conductivity, high thermal conductivity and intriguing mechanical strength, graphene can find great potential applications in the fileds of electronics, sensors and energy. In this thesis, the production of graphene via liquid-phase exfoliation of graphite was presented and its applications in the fields of metal nanoparticles based electrocatalysts and polymeric composites were discussed. The main contents are shown below.1. Graphite oxide (GO) and pristine graphene (PG) were synthesized by Hummers method and liquid-phase exfoliation method, respectively. The structure and morphology of GO and PG were investigated by FT-IR、XRD、TEM、XPS and Raman. The results showed that the surface of graphite oxide contained abundant oxygen functional groups that can allow for further functionalization of GO. However, the presence of excessive oxygen functional groups on GO surface severely disrupts the periodicity of sp2-hybridized carbon atom. Pristine graphene, with minimal oxygen functional groups and structure defects, retains its π-π conjugated structure of graphene. The pristine graphene was suitable for preparing high performance inorganic metal nanoparticles-based hybrids and polymer composites.2. A simple but effective supercritical fluid method was developed to deposit PtNi alloy nanoparticles with different molar ratios on carbon black (XC-72) and pristine graphene (PG), respectively. The structure and morphology of the composites were investigated by XRD、TEM、XPS and Raman etc. The results suggested that ultrafine Pt-based particles are homogeneously deposited on the surface of pristine graphene. The catalytic activity and stability of the catalysts for the oxidation of methanol were investigated by CV and CA tests at room temperature. The PtNi nanoparticles on pristine graphene exhibit excellent electrocatalytic activities for methanol oxidation as compared with those of commercial Pt/C and PtNi nanoparticles anchored on XC-72. Among all catalysts, optimal electrocatalytic activity and stability were found in Pt3Ni/PG. The supercritical method can be extended to prepare other high-performance metal or metal oxide/PG composites.3. A series of pristine graphene (PG)-reinforced polystyrene (PS) composites with different loadings of PG were prepared using solution mixing and subsequent flocculation method. The composites were characterized by SEM、TEM、DSC and DMA etc. The pristine graphene was found to be well dispersed in the polystyrene matrix. Compared with neat PS, the thermal properties of PS/PG composites significantly improved. The tensile tests indicated that addition of 0.5 wt% PG results in a 63.5% increment in tensile strength and a 77.4% improvement in Young’s modulus over pure PS. The enhancement in storage modulus also indicate that PG is an ideal filler for the polystyrene matrix...