Preparation,characterization And Photocatalytic Activities Of N-doped TiO₂ Nanotubes Arrays And Their Composites With SrTiO₃

Nanostructured TiO₂ materials are a n type semiconductor?Eg=3.0-3.2 eV?,which are applied to battery,the degradation of organic pollutants and water splitting to generate hydrogen due to their high photocatalytic activity,excellent chemical stability,low cost,nontoxicity and resistance to photocorrosion.Series of N-doped TiO₂ nanotube array were prepared by anodization method,the effect of NH4 F quantity,preparation voltage and calcination temperature on the morphologies,N-doping level,optical properties,photodegradation of organic dyes and photocatalytic activity of hydrogen evolution of N-TiO₂ NTAs were studied.N-TiO₂/SrTiO₃ composites were synthesized by hydrothermal method.The morphologies,crystal structures,light absorption and fluorescence emission of the as-synthesized samples were characterized by SEM,TEM,XRD,XPS,UV-Vis diffuse reflectance absorption spetra,PL spectra.The photocatalytic activity was studied by photodegradation of RhB and photocatalytic water splitting to generate hydrogen,and photocatalytic reaction mechanism were proposed.The main content of this thesis includes:A series of N-doped TiO₂ nanotube arrays were prepared by anodization method,changing the NH4 F quantity in glycol solution with ammonium fluoride,water,formamide and concentrated sulfuric acid.The morphologies,crystal structures,light absorption and fluorescence emission of the as-synthesized samples were characterized by SEM,TEM,XRD,XPS,UV-Vis diffuse reflectance absorption spectra and PL spectra.The photocatalytic activities were studied by photodegradation activity on RhB and photocatalytic water splitting to generate hydrogen.The effects of N-doping level on the morphology,photodegradation activity and photocatalytic activity of N-TiO₂ NTAs were studied.The formation mechanism,photodegradation activity on RhB and photocatalytic water splitting to generate hydrogen of N-doped NT-NAs were also discussed.It was found that with the increase of NH4 F content,the tube length increased firstly and then decreased,while the tube diameter hardly changed.The TiO₂ catalyst prepared using 0.2 g of NH4 F exhibits the highest photocatalytic activity due to the longest tube length?more active sites?and the lowest recombination rate of the photo-generated carriers.It was found the O₂-×and photogenerated holes were the active species responsible for photodegradation of RhB.N-TiO₂ NTAs were prepared by anodic oxidation method,and the microstructure and crystal structure of the nanotube arrays were controlled by changing the voltage and calcination temperature.The morphologies,crystal structures,light absorption and fluorescence emission of the as-synthesized samples were studied by SEM,XRD,UV-Vis diffuse reflectance absorption spectra,PL spectra.The photocatalytic activities were studied by photodegradation activity on RhB and photocatalytic water splitting to generate hydrogen.The results show that the photocatalytic activity of the catalyst on RhB and photocatalyticwater splitting to generate hydrogen were related to the voltage and the calcination temperature,N-TiO₂ NTAs prepared at 40 V voltage and calcination at 400°C exhibits the highest photocatalytic activity.In addition,the effects of noble metal doping and light source on the photocatalytic activity of N-TiO₂ NTAs were studied.The results show that the photocatalytic water splitting to generate hydrogen of N-TiO₂ NTAs was better under UV-visible light,and noble metal doping will enhance the photocatalytic activity.Particularly,0.13% Pd doped N-TiO₂ NTAs exhibits the highest photocatalytic activity.N-TiO₂/SrTiO₃ composites were synthesized by hydrothermal method using N-TiO₂ NTAs prepared at 40 V as the precursor.The effects of the reaction time and the order of calcination on the morphologies,crystal structures,optical properties and photocatalytic activity of the N-TiO₂/SrTiO₃ composites were studied.The results show that N-TiO₂ NTAs is gradually transformed into SrTiO₃ with increasing the reaction time,and the photocatalytic activity of the sample obtained at 2 h is the highest due to the remained tubular structure and the formation of N-TiO₂/SrTiO₃ heterojunction.In addition,the morphology of the N-TiO₂/SrTiO₃ composites after calcination was the smooth nanotube array,and the photocatalytic activity also became higher.