Semiconductor Or Graphene-based Composites Modified TiO₂Nanotube Arrays And Their Photocatalytic Application

Photocatalysis is an important and effective process for removing organicpollutants from wastewater. Among the photocatalyts, titanium dioxide （TiO₂）has been widely applied because of its non-toxicity, low cost andantiphotocorrosion. However, the utilization ratio of sunlight of TiO₂isrelatively low due to its wide band gap （3.0eV for the rutile）. Furthermore, thephotogenerated electron-hole pairs which are responsible for chemical reactionswith pollutants tend to quick recombination, and thus the photocatalyticapplication of TiO₂materials is greatly restricted. In this thesis, in order tosolve the above problems, as an electronics storage and transporter, graphenewas fabricated on the surface of TiO₂nanotube （TiO₂NTs） along withnarrow-band-gap semiconductor. In addition the TiO₂NTs modified with TiO₂nanoparticles were investigated. The modified TiO₂NTs photocatalystsenhanced the utilization rate of light absorption and greatly improved thephotocatalytic activity. The photocatalytic degradations of PCP and AO7overthe resulting photocatalysts were conducted to evaluate their photocatalyticproperties. The main research contents are as follows:（1） Preparation, characterization and photoelectric properties ofRGO/PbS-TiO₂nanotube arrays （RGO/PbS-TiO₂NTs） composite materials: asimple one-step electrodeposition method was proposed for the simultaneousfabrication of graphene and PbS nanoparticles on TiO₂NTs to obtain the ternarycomposite photocatalyst. The PbS nanoparticles were deposited on both theoutside and inside walls of the TiO₂NTs and also inserted between graphenenanosheets. The photoelectric test results show that compared with the bare orsingle modified TiO₂NTs, RGO/PbS-TiO₂NTs extended the visible-lightabsorption region, and increased the photocurrent density two times undersimulated sunlight and visible light （wavelength over420nm） irradiation.Meanwhile, the electron-hole recombination probability of the compositematerial was greatly reduced.（2） Investigation of photocatalytic degradation of PCP on RGO/PbS-TiO₂NTs: The PCP photocatalytic degradation effects over RGO/PbS-TiO₂NTsphotocatalyst were investigated. The results show the photocatalytic degradation rate of PCP on RGO/PbS-TiO₂NTs was affected by solution pHvalue and the initial concentration of PCP, and the optimum conditions is pH=8,and10mg/L of PCP. Under simulated sunlight irradiation, the degradationefficiencof PCP was almost100%within120min. The RGO/PbS-TiO₂NTsphotocatalyst was very stable after eight repeated experiments, indicative of theeffective suppression of photocorrosion of narrow-band-gap semiconductor.（3） Fabrication, characterization and photocatalytic application of TiO₂NTs modified with TiO₂nanoparticles: TiO₂nanoparticles was fabricated onTiO₂NTs though the potentiostatic deposition of TiCl3. The crystal structure,photoelectric chemical properties, and photocatalytic performance of themodified TiO₂NTs were studied. The results show the photocurrent density ofthe modified TiO₂NTs was1.7times that of the bare TiO₂NTs. Meanwhile, themodified photocatalyst exhibited a substantially increased adsorption to azodyes AO7and an enhanced photocatalytic removal efficiency of AO7.