Modification And Photocatalytic Application Of TiO₂Nanotube Array

Photocatalysis is one of the most promising technologies for treatingenvironment pollutions. As one of the most common photocatalysts, TiO2is widelyconcerned in photocatalytic application because of its chemieal stability, highcatalytic efficiency, nontoxicity, and low cost. However, the practical application ofTiO2is retarded by its wide band gap, high recombination rate of the photogeneratedelectron-hole pairs, poor adsorbability to most of organic contaminants, and poorrecovery. In this work, some TiO2nanotube array (TiO2NT)-based composites wereprepared to extend the absorption of TiO2NT to the visible spectrum region, improvethe separation effeciecy of photogenerated carriers, enhance the adsorptivity toorganic pollutants, and increase photocatalytic efficiency. The main research contentsare listed below:(1) Fabrication and characterization of TiO2nanoparticals-graphene-TiO2nanotube array (RGT/TiO2NT): TiO2NT was assembled with graphene oxide (GO)and TiO2nanoparticles by sol-gel method. Then the as-prepared composite wascalcined for3h at500℃under the anaerobic condition, in order to reduce the GOto reduced GO (RGO) and transform the crystalline of TiO2. The structure wasdetermined by SEM, TEM, and XPS. The results of SEM showed that TiO2nanoparticles were attached on the surfaces of both RGO sheets and TiO2NT.Interestingly, some RGO sheets stood on the surface of TiO2NT vertically, forming ahierarchical structure. As shown in the optical performance test, compared withunmodified TiO2NT, RGT/TiO2NT increased the optical absorption significantly anddecreased the recombination rate of elertron and hole.(2) Investigation of photodegradation of2,4-D on RGT/TiO2NT: thephotocatalytic properties of the RGT/TiO2NT were investigated through the2,4-Dphotocatalytic degradation. Compared with the neligible adsorption on unmodifiedTiO2NT, the adsorptivity of RGT/TiO2NT to2,4-D was dramatically enhanced. Thephotocatalyst exhibited nearly100%removal efficiency and80%removal rate ofTOC under simulated solar light irradiation. After five recyclings, the photocatalyticdegradation efficiency remained highly stable. Good stability and easy recoverydemonstrated the photocatalytic system to be a promising application for herbicide orother organic pollutant removal from water.(3) Fabrication and photocatalystic application of Ag2S/TiO2NT: Ag2S nanoparticles were decorated onto TiO2NT via a simple successive ionic layeradsorption. Rhodamine B was selected as the model molecules to test thephotocatalysts. Under the condition of simulated sunlight, the effect of Ag2S contenton the photodegradation of the rhodamine B was investigated. Compared withunmodified TiO2NT, Ag2S/TiO2NT showed higher photocatalytic activity. However,the photocatalysis stability of Ag2S/TiO2NT was not ideal.