Synthesis Of Carbon-based Composites And Their Application In The Hydrolysis Of Ammonia Borane

Carbon-based nanomaterials have attracted much attention due to their unique structure and excellent physical and chemical properties. Graphene and carbon nanotubes(CNTs) have excellent electrical, optical, thermal, mechanical properties and large specific surface area. In recent years, transition metal nanoparticles and graphene or CNTs hybrids were widely used as catalysts for the hydrolytic dehydrogenation of ammonia borane. Graphene and CNTs were considered as ideal supporting materials with metal nanoparticles loaded on the surface of graphene or CNTs. These composites replace the traditional precious metals by reducing the cost and improving the reusability. Synchrotron radiation techniques are also used to characterize the electronic structure and chemical interaction of carbon-based composites.In this thesis, transition metal nanoparticles and graphene or CNTs composites were prepared and used as catalysis for hydrolytic dehydrogenation of ammonia borane, and their catalytic activities have been studies. Main contents are shown as below:Firstly, graphene doped with various elements was successfully synthesized by hydrothermal method, and on this basis, metal nanoparticles were dispersed on the surface of graphene. By this method, the doped graphene has significant threedimensional structure with various holes. However, preliminary tests of the hydrolysis of ammonia borane showed that their reaction time were too long, due to the low loading content of metal.In addition to the hydrothermal method, another convenient chemical method was used to synthesize the composites. The TOF value of the produced nickel and cobalt bimetallic graphene composite(Ni0.5Co-G) is a good value of 14.10 mol mol-1 min-1, and the nickel-cobalt bimetal shows a synergistic effect that facilitates the catalytic performance. Also, Ni0.5Co-G shows excellent reusability keeping 55.11% catalytic activity after fifth catalytic reaction. Ni0.5Co-G has a great potential in the development of solid catalyst.We also use wet chemical method to synthesize metal nanoparticles and CNTs composites. We choose two kinds of CNTs as the metal substrates. After comparison, the outside diameter of CNTs has a great influence on the catalytic performance. Moreover, the electronic structure of individual MWCNTs was studied by scanning transmission X-ray microscopy(STXM). Although transmission electron microscope(TEM) images show that MWCNTs are all clean and straight, the inside damage of MWCNTs can be detected by comparing the C K-edge XANES features. A long time TEM measurement may also lead to the inside damage.