Preparation And Properties Of Supported Titania Nanotubes/Nanocrystals Composite Photocatalysts

With the development of global industrialization, pollution has become increasingly seriously. Environmental protection and sustainable development are the primary problems facing mankind. Photocatalytic degradation technique is a kind of green environmental friendly technology, which refers to using the solar energy to decomposite contaminants into CO2, H2O and other harmless substance. TiO2 is an important semiconductor photocatalysis material due to its small diameter, large surface area, high photocatalytic activities, chemical stability and low cost. Among the various TiO2-based materials, the one-dimensional tubular TiO2 nanotubes (refers to TNTs) which present an end opened, middle hollow structure. It has strong adsorptive capacity but very low photocatalytic activity. Research has been focused on the composite photocatalysts combining the high adsorptive capacity with the enhanced photocatalytic efficiency. This thesis has prepared a kind of supported titania nanotubes/nanocrystals composite with high photocatalytic activity through surface modification.TNTs were synthesized via hydrothermal method using P25 as the raw material. The Pt-supported titania nanotubes/nanocrystals composite photocatalysts (refers to Pt/TNNs) were prepared via one-step method involved the vapor phase hydrolysis setup, where TNTs were added into the ethanol solution containing H2PtCl6·6H2O and C6H8O7 (as the reductant). The photocatalytic activities of the as-prepared catalysts were investigated by the degradation of acid red G (ARG) and methylene blue (MB). The following conclusions were obtained:The as-prepared TNTs were 5-8nm in diameter,200-400nm in length and had a specific surface area as high as 463m2/g. The Pt nanoparticles in crystallite size of 4nm were uniformly dispersed onto the surface of remaining TNTs and anatase TiO2 nanocrystals with the crystallite size of 8nm derived from the transformation of TNTs, and the composite photocatalysts kept a specific surface area of more than 216m2/g. During the water vapor treatment, some of the nanotubes were transformed into anatase TiO2 nanocrystals and a small amount of TNTs were kept as the tubular morphologies, thus the composite had a higher adsorptive capacity. The photocatalytic activity of Pt/TNNs was evaluated by the degradation rate of ARG and MB under UV irradiation. The results showed that Pt/TNNs obtained via water vapor treatment at 120℃exhibited much higher photocatalytic efficiency compared to the pristine TNTs. But the photocatalytic efficiency dropped after the loading amount was higher than 2.5wt%. The thesis prepared Au supported titania nanotubes/nanocrystals composite (refers to Au/NTs), where TNTs were added into the ethanol solution containing HAuCl4·4H2O and NaBH4 (as the reductant). The XRD and TEM results showed that Au nanoparticles in crystallite size of 10nm were uniformly dispersed onto the surface of TNTs and the composite had good crystallization as well. The specific surface area of Au/NTs dropped greatly after water vapor treatment at 120℃. It exhibited good adsorption to dyes MB and improved photocatalytic efficiency compared to Pt/TNNs.We synthesized TiO2 supported titania nanotubes/nanocrystals composite (refers to NT/NC) using TBOT as the procuser via vapor hydrolysis method. It exhibited high photocatalytic activity compared to the pristine TNTs. The thesis prepared Pt, Au, TiO2 supported titania nanotubes/nanocrystals composites via vapor hydrolysis method. TNTs were partly transformed into anatase TiO2 nanocrystals during the process and the composite remained a high specific surface area. This kind of compound photocatalysts exhibited good adsorptive capacity and high photocatalytic activities.