Catalytic Reactivity of Copper Surfaces in the Synthesis of Carbon Nanostructures

Graphene and carbon nanotubes exhibit extraordinary and diverse properties, and therefore these nanomaterials are finding an increasing number of applications in many industries. However, the major obstacle in the integration of these nanomaterials into practical devices is the inability to cost-effectively produce them in high qualities and large scales, and tailor them towards specific needs. The catalytic chemical vapor deposition (CCVD) is currently the most common method of synthesis of these nanomaterials, and their associated growth mechanism is a subject of intense study. The central theme to these studies is elucidating how the many different parameters such as temperature, catalyst and substrate type, and carbon source gas type and composition may affect the resulting structure and properties of these nanomaterials. This study focuses upon the earliest stages of nucleation whereby the carbon-containing precursor gas dissociates on the catalyst surface and forms carbon networks, and how this stage may be affected by environmental parameters. The research presented here was conducted using first-principles based kinetic Monte Carlo simulations and other density functional theory-based theoretical methods to characterize catalytic and growth mechanisms of carbon nanostructures mainly using copper (Cu) as the catalyst, although for comparison, other commonly used transition metals have also been studied alongside Cu. Results obtained explain, from an atomistic level perspective, why the practice of flowing hydrogen gas alongside methane in the CCVD method is important for methane dehydrogenation. Results also show that the presence of surface oxygen facilitates methane dehydrogenation on Cu surfaces and inhibits that on nickel surfaces. The decomposition of acetylene on supported Cu and cobalt nanoparticles and the effects of the catalyst support and support doping are also discussed. Some discernible differences are found in the performance of the two metal nanoparticles. In addition, the effect of temperature on the coalescence of small graphene islands on Cu, as studied in this dissertation, provides new insights into graphene growth mechanisms