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Controllable Preparation And Photocatalytic Activity Of Nanostructured TiO2 Photocatalysts

Posted on:2008-03-24Degree:DoctorType:Dissertation
Country:ChinaCandidate:H G YuFull Text:PDF
GTID:1101360215492219Subject:Materials Physics and Chemistry
Abstract/Summary:PDF Full Text Request
Semiconductor TiO2 photocatalysts have promising applications in the wastewater treatment, air purification, bacillus resistance, mist prevention andself-cleanness. In this dissertation, valuable explorations have been carded out onthe synthesis of highly active TiO2 photocatalysts, the immobilization of TiO2nanoparticles, the facile preparation of one-dimensional TiO2 hollow structures andNa-free anatase TiO2 films with highly photocatalytic activity. The main pointscould be summarized as follows:In chapter 2, a new synthetic way has been developed to prepare TiO2nanoparticles with a high specific surface area in order to obtain the highly activeTiO2 photocatalysts. After the well-controlled calcination of titanatenanotubes/nanowires or hydrothermal post-treatment of titanate nanotubes, highlyactive TiO2 nanoparticle photocatalysts could be obtained. Moreover, the advantagesof high specific surface area and pore volume of the titanate nanotubes/nanowirescould be well preserved by these methods, resulting in the enhancement ofphotocatalytic activity.In chapter 3, it is well known that powder photocatalysts are difficult to beseparated completely from a slurry system after photocatalytic reaction and that TiO2film photocatalysts show a low photocatalytic activity due to their limited specificsurface areas. To overcome the shortcomings of powder and film photocatalysts,anatase TiO2 nanoparticles were uniformly coated on the surface of titanate nanorodsor nanotubes via a simple solution route at low temperature (<80℃). Moreover,anatase TiO2 particles were uniformly and dispersedly deposited on the surface ofglass fibers using a similar method. It was found that the immobilized TiO2nanoparticles, which could be readily separated after photocatalytic reaction, not onlyhave a large surface area and keep high photocatalytic activity, but also can avoid thedisadvantages of TiO2 powdered photocatalysts. Therefore, these novel TiO2photocatalysts can be expected to bring some new opportunities in the application ofhighly active TiO2 nanoparticles. Moreover, low-temperature technology allows TiO2to be deposited on the substrates that might not be chemically or mechanically stable at high temperatures, which would extend the used areas of TiO2 photocatalysts.In chapter 4, usually, templated methods include two important steps: thecoating of nanocrystals on the surface of the templates and the removal of templates.In this study, one-dimensional TiO2 hollow structures, based on the template-directeddeposition and then in situ template-sacrificial reaction (or dissolution), wereprepared by a one-step template method using vanadium oxide nanobelts as thetemplates. The coating of TiO2 nanoparticles on the surface of the templates wasaccompanied with the dissolution of vanadium oxide nanobelts by HF producedduring the hydrolysis of TiF4 in the reaction solution. The photocatalytic activityexperiment indicated that the prepared one-dimensional TiO2 hollow structures,which could be readily separated from a slurry system after photocatalytic reaction,exhibited obvious photocatalytic activity for the photocatalytic degradation of methylorange solution. This work may provide new insights into preparing other hollowoxide structured materials.In chapter 5, to prevent the negative effect of Na+ ions on the photocatalyticactivity, many methods such as pre-coating SL-glass with SiO2 layers to prevent thediffusion of Na+ ions or soaking the calcined TiO2 films into an acid aqueous solutionto exchange Na+ ions, have been reported. In this study, Na-free anatase TiO2 filmwas prepared on soda-lime glass (SL-glass) by a one-step, low-temperature method. Itwas found that the as-prepared TiO2 film before calcination showed a higherphotocatalytic activity than the calcined sample (500℃). Thus, the Na-free anataseTiO2 films deposited on SL-glass by this method would be quite useful asself-cleaning or indoor air cleaning windows.
Keywords/Search Tags:TiO2, anatase, titanate, photocatalysis, specific surface area, hollow structure, thin film, immobilization
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