GRAPH-CNTS-CAT · Intercalated Graphene Carbon Nanotubes for Heterogeneous Catalysis

Intercalated Graphene Carbon Nanotubes for Heterogeneous Catalysis

The objective of the project was to find a generalised approach for the preparation of graphene-carbon nanotubes composite materials and to explore their use in heterogeneous catalysis. The production of novel hybrid carbon-based materials as heterogeneous catalysts will contribute a novel approach in the science and technology of catalysis. The surface physico-chemical and chemical properties can be tailored by functionalising graphene sheets and/or carbon nanotubes and/or intercalating other species in the pores. The achievement of high catalytic turnover, selectivity towards a substrate could also lead to an innovative 'green' technology for pollution control. These novel graphene/CNTs composite materials were characterised by X-ray photoelectron, infrared and, electron paramagnetic resonance spectroscopies. A structural / morphological study was conducted by X-ray diffraction. Their catalytic activity was evaluated using simple hydrogenation reactions of olefins in liquid phases. List of keywords: Graphite oxide, graphene, carbon nanotubes, functionalisation, catalysis, metals Work performed and results. A. Preparation of graphene, oxide-graphene Preparation of GO: Employing the Brodie method consisting in an extensive chemical attack of graphite crystals to introduce oxygen-containing defects in the graphite planes and subsequent exfoliation, the H2O-soluble graphene oxide (GO) was prepared. This material could also be used to synthesise organo-graphene oxide derivatives by reacting GO with alkylamine molecules (octa-decyl-amine, etc). B. Insertion of functionalised carbon nanotubes (CNTs) between graphene oxide layers After preparing the GO as described in objective, one can proceed with the insertion of functionalised CNTs. Insertion of functionalised CNTs in graphene oxide: To find the best synthetic conditions several composite materials with different CNTs/GO ratio were prepared by intercalation chemistry. The characterisation of the composites showed that with increasing CNTs/GO ratio the GO first partially and then fully exfoliates when the CNT content reached 15 %. The exfoliation was not originally foreseen as an objective but an unexpected result which we decided to exploit in the next steps. Then, the reduction of the composite material with NaHB4 was done. The XPS characterisation showed that the reduced material contained small amounts of oxygen moieties. Layer-by-layer synthesis of CNTs sandwiched between GO layers using the Langmuir-Schaefer approach: To build two-dimensional (2D) GO/CNTs and clay/CNTs nanocomposite, a modified Langmuir-Blodgett (LB) method (known as Langmuir-Schaefer method) was employed. The host group has recently applied this technique to insert a variety of molecular species between clay nano-sheets and to prepare a high quality GO-surfactant thin film. Based on this expertise, I synthesised a clay/CNTs thin film. GO/CNTs composite materials decorated with metal cations CNTs(M): Functionalised CNTs containing active groups to bind metals were used to bind transition metals like Fe, Cu, Mn. The XPS characterisation of these metal-decorated CNTs showed that the metal ions were successful attached to the CNTS surface in form of metal oxides, namely Fe2O3 in the case of Fe, CuO in the case of Cu and MnO for Mn. After having achieved a better understanding about the structure and chemistry of the GO/CNTs nanocomposite materials, GO/CNTs(M) were prepared. The new nanocomposite materials were fully characterised. The results shows that in this case the GO was exfoliated after the intercalation of the CNTs(M). The chemical state of metal remains unaltered to the nanocomposite material. C. Heterogenous catalysis Preliminary experiments aimed at establishing the catalytic efficiency of the prepared materials were already performed.

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