Photocatalytic And Field Emission Properties Of SnO₂/graphene Composites

Graphene is a single-layer carbon material composed of sp2-bonded carbon atoms arranged in a honeycombed network with six-membered rings. Graphene has unique properties such as high elasticity, outstanding mechanical strength, high theoretical specific surface area of 2600 m-2·g-1, and rapid heterogeneous electron transfer. High thermal conductivity(~ 5000 W·m-1·K-1), making it a promoting material in optoelectronic devices. Stannic oxide(SnO2) nanomaterial as a stable n-type wide band gap of 3.6eV semiconductor has been wide used as gas sensors, lithium rechargeable batteries and photocatalytic degradation of organic dyes. In this thesis, we have investigated the preparation, the field emission and photocatalytic properties of SnO2/graphene composites.The relationship between the structure and property of nanocomposite materials is very significant. Precisely controlling the sizes, dimensionalities and morphologies at nanoscaled level may be critical for the property improvement of materials and provide experimental basis for further systematic research.In this work, a large-scale growth of different morphologies of SnO2 on graphene oxide(GO) and graphene was achieved by hydrothermal route. A series of analytical techniques, such as: X-ray diffractometer(XRD), scanning electron microscope(SEM), X-ray energy dispersive spectrometer(EDS), Raman spectra, UV-vis diffuse reflectance spectra(DRS) techniques and transmission electron microscopy(TEM) were applied to characterizing the composition and morphology of samples.1. Stannic oxide(SnO2) microspheres have been successfully synthesized on graphene oxide sheets(GOs) by a hydrothermal method, and its optoelectronic properties have been studied. The concentration of ethanol plays an important role in the morphologies and optoelectronic properties of SnO2 microspheres. A large number of SnO2 microspheres with smooth surface are grown on GOs when the concentration of ethanol is 25%. While the concentration is added to 50%, SnO2 microspheres with rough surface are formed. When the concentration is further increased to 75%, dandelion-like SnO2 microspheres are grown on GOs. The results of XRD revealed that the as-grown SnO2 microspheres have tetragonal rutile structure. In addition, the optical properties of SnO2/GOs composites are investigated. An obvious absorption peak is observed at 554 nm for the dandelion-like SnO2 microspheres in the UV-Vis spectrum.2. Allium mongolicum-like, turfgrass-like and needle-like Stannic oxide(SnO2) nanograsses have been successfully synthesized on graphene oxide sheets(GOs) by a hydrothermal method. The field emission(FE) properties of SnO2 nanograsses/GOs were measured and found to be strongly influenced by the morphologies of SnO2. Due to they have greater density, high aspect ratio, nano-sized sharp corners and they are more close to perpendicular to the surface of GOs. The results show that needle-like SnO2 nanograsses composed of nanorods have best FE properties.