Materials World Network: Novel Catalyst Systems for Carbon Nanotube (CNT) Synthesis and their Underlying Mechanisms

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Chemical vapor deposition (CVD) techniques employing nano-particulate catalysts and catalyst films have proven to be versatile and effective methods for synthesizing carbon nanostructures, such as nanotubes (CNTs) and graphene. CVD enabled extensive investigation of these structures as well as opened routes towards their application in integrated circuits, energy storage, transparent conductors, thermal management surfaces, hierarchical composites, sensors, drug delivery and biomimetics. Despite these successes, the detailed mechanisms of catalytic CVD remain poorly understood and the CVD process lacks deterministic control, in particular regarding CNT chirality. Common catalysts, such as Ni and Fe, are active in their metallic state and hence are prone to coarsening and support interactions at the elevated temperatures required for CVD. We recently demonstrated that nano-particulate zirconia catalyses CNT growth at moderate temperatures, whereby it neither reduces to a metal nor forms a carbide. The low reactivity and limited restructuring of oxides promise a high level of control for the CVD process. We propose to study a range of oxides as CVD catalysts. We plan to use in-situ X-ray photoemission spectroscopy and environmental transmission electron microscopy to explore the mechanism(s) of graphene formation and nanotube nucleation on pre-treated oxide films and size-selected oxide nanoparticles. We will analyse the chiral selectivity of oxide-assisted CNT CVD and explore the possibility of large area graphene CVD on oxide films.