Photocatalytic Property of TiO2 Films Deposited by Pulsed DC Magnetron Sputtering

TiO2 thin films were prepared by DC magnetron sputtering with the oxygen flow rate higher than the threshold. The film deposited for 5 h was of anatase phase with a preferred orientation along the <220> direction, but the films deposited for 2 and 3 h were amorphous. The transmittance and photocatalytic activity of the TiO2 films increased constantly with increasing film thickness. When the annealing temperature was lower than 700℃, only anatase grew in the TiO2 film. TiO2 phase changed from anatase to rutile when the annealing temperature was above 800℃. The photocatalytic activity decreased with increasing annealing temperature.     

Effect of Substrate Pretreatment on Controllable Growthof TiO2 Nanorod Arrays

Well-aligned TiO2 nanorod arrays(TNAs) were prepared on the pretreated quartz substrates.The effect of the pretreatment conditions on the growth of TNAs was systematically investigated by X-ray diffraction(XRD),field-emission scanning electron microscopy(FE-SEM) and high-resolution transmission electron microscopy(HRTEM).It is demonstrated that the pre-coating TiO2 crystal seeds on the substrates can greatly improve the growth orientation of TNAs.Rutile TiO2 crystal seeds induce the nucleation and growth of TNAs more preferably than the anatase TiO2 seeds.The growth density and diameter distribution of TNAs strongly depend on the TiO2 crystal seeds density.It is proved that TNAs with different morphologies can be controllably synthesized by using hydrothermal approach by pretreating substrates.The photocatalytic activity of TNAs was investigated by measuring the photodegradation rate of methyl blue aqueous solution under UV irradiation(254 nm).And the results show that TNAs with large growth density and small diameter size exhibit relatively higher photocatalytic activity.     

Synthesis,Surface Characterization and Photocatalytic Activity of TiO2 Supported on Almond Shell Activated Carbon

Three types of photocatalysts were synthesized by metal organic chemical vapor deposition and impregnation methods using the almond shell activated carbon as support. These photocatalysts denoted by （TiO2/ASAC （V）, TiO2/ASAC （11） and TiO2/ASAC （12）） were characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, diffuse reflectance spectroscopy （DRS） and nitrogen adsorption-desorption isotherms. SEM observation shows that TiO2 was deposited on activated carbon surface. XRD results confirm that TiO2 existed in a mixture of anatase and rutile phases. The DRS spectra show the characteristic absorption edge of TiO2 at approximate 380 nm corresponding to the optical band gap of 3.26 eV. Besides, FTIR spectrum indicated the presence of （Ti-O） groups. The specific surface area of photocatalysts decreased drastically in comparison with the original activated carbon. The catalysts were very efficient for the photodegradation of total organic carbon （TOC） from industrial phosphoric acid solution under UV irradiation. The kinetics of photocatalytic TOC degradation was found to follow a pseudo- first-order model. The prepared TiO2/ASAC showed high photoactivity for the photodegradation of TOC in the following order： TiO2/ASAC （V） 〉 TiO2/ASAC （11） 〉 TiO2/ASAC （12） 〉 ASAC 〉 TiO2 （P25）.     

Preparation and Characterization of Buoyant Nitrogen-doped TiO2 Composites Supported by Fly Ash Cenospheres for Photocatalytic Applications

Fly ash cenospheres(FACs) coated with nitrogen-doped TiO2(N-TiO2) composites were prepared by the sole gel method for use as photocatalysts.The photocatalytic activity and kinetics of the composites produced at different calcination temperatures and with different nitrogen doping contents were studied under visible light irradiation by monitoring the environmental degradation of methylene blue(MB).The MB degradation ratio of N-TiO2/FAC(25%,450℃) was 10% higher than that of N-TiO2 and 40% higher than that of TiO2/FAC.These N-TiO2/FAC composites floated in water and could be recovered after the photocatalytic reaction by phase separation.     

Synthesis,Characterization and Photocatalytic Activity of TiO_2 Film/Bi_2O_3 Microgrid Heterojunction

TiO2 film modified by Bi2O3 microgrid array was successfully fabricated by using a microsphere lithography method.The structure and morphology of TiO2 film,Bi2O3 film and TiO2 film/Bi2O3 microgrid heterojunction were characterized through X-ray diffraction,atomic force microscopy and scanning electron microscopy.The optical transmittance spectra and the photocatalytic degradation capacity of these samples to rhodamine B were determined via ultraviolet-visible spectroscopy.The results indicated that the coupled system showed higher photocatalytic activity than pure TiO2 and Bi2O3 films under xenon lamp irradiation.The enhancement of the photocatalytic activity was ascribed to the special structure,which could improve the separation of photo-generated electrons and holes,enlarge the surface area and extend the response range of TiO2 film from ultraviolet to visible region.     

Preparation and Characterization of Nucleus/Shell TiO2/HAP Complex Nanophotocatalyst

A rapid and more efficient method was developed to prepare nucleus/shell titania/hydroxyapatite （TiO2/HAP） complex nanophotocatalyst. Hydroxyapatite （5 μm） which had been dissolved with 0.1 mol/L HCI was formed on the surface of the nanosized anatase titania powders by increasing the pH value of the solution at 90℃ in the water bath for only several hours .The microstructure and morphology of the resulting sample were investigated by X-ray diffraction （XRD）, Fourier-transform infrared spectroscopy （FT-IR）, scanning electron microscopy （SEM）, energy dispersive spectrum （EDS） and atomic force microscope （AFM）. The results indicated that nucleus/shell structural TiO2/HAP was formed in our experiments, and the thickness of the coating layer was about 5 nm. Photocatalytic decomposition of methyl orange was utilized to test the photocatalysis of the resulting samples and the result was compared with that of pure anatase titania powders （about 20 nm）. It was shown that the photocatalytic activity of the sample was not decreased due to the coating of HAP.     

陶瓷靶射频磁控溅射TiO2薄膜的制备和光催化特性

Transparent titania thin films were prepared on glass substrates by radio frequency magnetron sputtering from TiO2 ceramic target. The structure and morphology of those films with different sputtering power and substrate temperature has been measured with X-ray diffractometer (XRD) and atomic force microscope (AFM). It was found that the films were anatase and a mix of anatase-rutile with different condition. The transmission of the films has been studied by using UV-VIS-NIR spectrometer. It shows absorption edge has a little red shift with the increase of sputtering power and substrate temperature. The photocatalytic activity of the films was tested on the degradation of Rhodamine B solution. T.he highest degradation efficiency in our experiment was obtained in the film deposited at 550℃ and 130W.     

Effect of Anodization Parameters on Morphology and Photocatalysis Properties of TiO_2 Nanotube Arrays

Highly ordered TiO2 nanotube arrays were fabricated via electrochemical anodization of high purity Ti foil in fluoride-containing electrolyte. The effects of applied anodization potential, anodization time on the formation of TiO2 nanotube arrays and the photocatalytic degradation of methylene blue(MB) were discussed. The TiO2 nanotube arrays calcined at 500 °C for 2 h show pure anatase phase. The pore diameters of TiO 2 nanotube arrays can be adjusted from 30 to 90 nm using a different anodization voltage.Anodization time mainly influenced TiO 2 tube length, and by increasing the anodization time, the nanotube length became longer gradually. When the anodization potential was 40 V, the average growth rate of TiO 2 nanotube was about 4.17 μm/h. Both anodization potential and time had important effects on the photocatalytic efficiency. The TiO 2 nanotube arrays obtained at anodization potential of 40 V for 1 h showed the best photocatalytic degradation ratio of MB.     

Synthesis of Mesoporous Anatase TiO_2 Sphere with High Surface Area and Enhanced Photocatalytic Activity

Mesoporous anatase TiO_2 spheres with high surface area(119 m~2g~(-1)) were successfully synthesized via a facile and green template-free method. The prepared TiO_2 was characterized by X-ray diffraction(XRD),N_2 adsorption, scanning electron microscopy(SEM), transmission electron microscopy(TEM) and UV–vis absorbance spectra. It was found that the prepared TiO_2 is characterized by pure anatase phase, which shows uniform spheres and has a typical mesostructure with a high specific surface area and a large pore volume. The effects of complexant(acetylacetone) amount, crystallization temperature and calcination temperature were also investigated. Based on the results, a sketch for the preparation of mesoporous TiO_2 was proposed. First, complex formed between tetrabutyl titanate and acetylacetone in ethanol. After introduction of aqueous of ammonia sulfate and urea, hydrolysis of tetrabutyl titanate would occur slowly,and sol of TiO_2 was formed. Then, crystallization proceeded under hydrothermal conditions. Calcination process favored the formation of bigger TiO_2 crystal through combining of the small crystals in TiO_2.This led to the formation of bigger mesopores between TiO_2 crystals. Photocatalytic activity of the prepared TiO_2 was evaluated by decomposition of methyl orange.     

Enhanced Photocatalytic Activity in p-NiO Grafted n-TiO_2 Porous Coatings

We synthesized NiO-loaded TiO_2 porous p-n junctions by electrophoretic enhanced micro arc oxidation(EEMAO) technique which is a relatively simple and new method for producing composite coatings.Phase structure,chemical composition,and surface morphology of the NiO—TiO_2 coatings were investigated by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and scanning electron microscopy(SEM) techniques,respectively.Photocatalytic efficiency of the samples was studied through measuring the decomposition rate of 4-chlorophenol under UV irradiation.Results showed that the coatings mainly consisted of anatase,rutile,and nickel oxide phases.It was observed that a finer surface morphology,i.e.smaller pores,was obtained at lower voltages.Besides,the amount of nickel oxide loaded to the TiO_2 host increased with the voltage.The NiO-TiO_2 composite coatings showed a higher photoactivity than pure TiO_2 coatings revealing the effective role of NiO in decreasing the recombination rate of photogenerated electrons and holes.The maximum photocatalytic reaction rate constants for TiO_2and NiO—TiO_2 samples were obtained as 0.0064 and 0.0131 min~(-1),respectively.We also found that there was an optimum concentration of NiO where a maximum photocatalytic activity was achieved.A correlation between growth variables,structure,and photocatalytic efficiency was established.     

Adsorption and photocatalytic decomposition of organic molecules on carbon-coated TiO2

Carbon-coated anatase TiO₂ samples were prepared from the mixture of poly vinyl alcohol (PVA) and commercial TiO₂ (P-25) with different mass ratios and heating temperatures. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDX), transmission electron microscope (TEM), and nitrogen adsorption analyses. The adsorption properties and photocatalytic activity of commercial and carbon-coated TiO₂ catalysts were compared for the oxidation of methylene blue (MB) and bisphenol-A (BPA). It was interesting to find that the transition from anatase to rutile was suppressed by carbon coating of TiO₂ at high temperature up to 800 °C. The carbon-coated TiO₂ samples have a higher surface area and a greater adsorption amount than commercial P-25 because of the thin layer of carbon that covered TiO₂. It was also observed that the photodecomposition efficiency was dependent on the crystallinity of the carbon-coated sample.     

Simple fabrication of carbon/TiO2 composite nanotubes showing dual functions with adsorption and photocatalytic decomposition of Rhodamine B

Carbon/TiO2 composite nanotubes were fabricated via a very simple electrospinning process and their dual functionalities of adsorptivity and photocatalytic activity were evaluated using Rhodamine B (RhB) as a model organic pollutant. A poly(vinyl alcohol) (PVA) aqueous solution was directly electrospun into a coagulation bath containing titanium (IV) tetraisopropoxide (TTIP) solution so that PVA-core/TiO2-shell composite nanofibers were formed through the in situ sol-gel reaction of TTIP. The carbon/TiO2 composite nanotubes were then fabricated by heat treatment of composite nanofibers under nitrogen atmosphere. By using several characterization methods, we confirmed that the resultant nanotubes consisted of anatase TiO2 nanocrystallites embedded in a carbonaceous matrix. The prepared nanotubes exhibited fast adsorption of RhB with high capacity compared with a commercial porous carbon, and they also showed the photocatalytic decomposition activity for the dye molecules under UV irradiation comparable to the degradation by P-25 and ST-01 (commercial TiO2). Finally, the carbon/TiO2 composite nanotubes exhibited several cycle performances of adsorption-photodegradation for RhB. This indicates that the composite nanotubes can adsorb and photodecompose organic pollutants repeatedly without additional activating processes.     

热处理温度对TiO2/SiO2复合气凝胶光催化性能的影响

采用溶胶–凝胶法在常压下经不同温度热处理制备了TiO2/SiO2复合气凝胶光催化剂,利用XRD、TGA和BET等手段对其微观结构进行表征,以甲基橙溶液光催化降解实验评价其光催化性能,研究了热处理温度对TiO2/SiO2复合气凝胶的微观结构及光催化性能影响规律.结果表明:随着热处理温度升高,TiO2/SiO2复合气凝胶中锐钛矿结晶度升高,晶粒尺寸增大,比表面积减小,使TiO2/SiO2复合气凝胶对甲基橙溶液的光催化降解活性呈现先升后降的变化趋势.当热处理温度为700℃左右,紫外光照20 min TiO2/SiO2复合气凝胶对甲基橙溶液的降解率达到95.4%.     

TiO_2微球的制备及N掺杂改性研究

通过水热结合热处理法制备了N掺杂和未掺杂的表面粗糙的TiO2微球。结果表明,N掺杂将TiO2微球的光谱吸收范围拓宽到了可见光区,光谱吸收能力增强和氧空位增多是提高TiO2微球光催化活性的主要积极因素,结晶度下降和孤立的N 2p能级对光生载流子的捕获起着次要的负面作用。     

Electron beam irradiation effect on the photocatalytic activity of TiO2 on carbon nanofibers

The electron beam (EB) irradiation effects of TiO2 deposited on carbon nanofibers (CNFs) were studied aiming the improvement of the photocatalytic activity. The EB irradiation contributed to an increase in crystallinity of the anatase resulting an improvement of the photocatalytic activity through the oxidation (ionization) of the doped TiO2 and leading to uniform distribution TiO2 particles on the CNFs surface. The photoactivity of the catalyst was measured by the decoloration of the methylene blue (MB) with time under UV irradiation.     

Preparation and characterisation of TiO2 nanoparticle and titanate nanotube obtained from Ti-salt flocculated sludge with drinking water and seawater

This study aimed to prepare and characterise titanium dioxide (TiO2) nanoparticles and titanate nanotubes produced from Ti-sat flocculated sludge with drinking water (DW) and seawater (SW). The Ti-salt flocculated sludge from DW and SW was incinerated at 600 degrees C to produce TiO2 nanoparticles. XRD results showed that the anatase TiO2 structure was predominant for TiO2 from DW (TiO2-DW) and TiO2 from SW (TiO2-SW), which were mainly doped with carbon atoms. Titanate nanotubes (tiNT) were obtained when TiO2-DW and TiO2-SW were hydrothermally treated with NaOH solution. Structure phase, shape, crystallisation and photocatalytic activity of tiNT were affected by the incineration temperature and the amount of sodium present in different tiNT. The tiNT doped with thiourea incinerated at 600 degrees C presented anatase phase, showing a high increase of the degree of crystallisation with nanotube-like structures. The photocatalytic activity of these photocatalysts was evaluated using photooxidation of gaseous acetaldehyde. Thiourea doped tiNT-DW and tiNT-SW showed similar photocatalytic activity compared to commercially available TiO2-P25 under UV light and indicated a photocatalytic activity under visible light.     

铁氮共掺杂TiO2光催化剂的制备及光催化性能

采用溶胶-凝胶法与微波合成法相结合制备铁氮共掺杂的TiO2光催化剂。通过XRD、FT-IR、UV-Vis、PL等对Fe-N-TiO2样品进行表征和分析,并以亚甲基蓝（MB）作为目标降解物,考察经不同温度热处理及不同掺铁量的样品对MB的降解效果。结果表明所制备的样品在700℃热处理5h后为锐钛矿相与金红石相混晶,样品的吸收阈值波长向可见光红移约45nm。铁氮共掺杂抑制了样品从锐钛矿相向金红石相的转变,提高了TiO2的光催化活性。在普通日光灯下,热处理温度为600℃、掺铁量与TiO2摩尔比为1︰200条件下制备的样品,其光催化活性明显高于Degussa P25。     

Enhanced activity of bismuth-compounded TiO(2) nanoparticles for photocatalytically degrading rhodamine B solution

TiO(2) nanoparticles compounded with different amounts of bismuth were prepared by a sol-gel method, and the effects of compounding bismuth on the phase transformation, photoinduced charge separation and photocatalytic activity for degrading rhodamine B solution were mainly investigated, along with enhancement mechanism of photocatalytic activity of TiO(2) nanoparticles by compounding bismuth species. It can be confirmed that, by means of X-ray diffraction (XRD), surface photovoltage spectroscopy (SPS) and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), compounding bismuth can extend the optical response, and effectively inhibit the phase transformation process from anatase to rutile, consequently greatly improving the anatase crystallinity so as to promote the photoinduced charge separation. These factors are responsible for the increase in the photocatalytic activity of TiO(2) compounded with an appropriate amount of bismuth species.     

Synthesis of nano titania particles embedded in mesoporous SBA-15: characterization and photocatalytic activity

Supported nanocrystalline titanium dioxide (TiO2) has been prepared by a post-synthesis step via Ti-alkoxide hydrolysis through the use of mesoporous SBA-15 silica. TiO2/SBA-15 composites with various TiO2 loading have been prepared and characterized by X-ray diffraction, nitrogen adsorption, Fourier transform infrared spectroscopy and diffusive reflective UV-vis spectroscopy. The addition of mesoporous SBA-15 prevents the anatase to rutile phase transformation and the growth of crystal grain. TiO2 did not block the SBA-15 pores, and their surface was fully accessible for nitrogen adsorption. Calcination in air of the composites up to 800 degrees C did not change the nanocrystal phase and slightly increased the domain size from 5.0 to 7.5 nm, indicating that the anatase TiO2 grains in the mesostructures have a relatively high thermal stability and proper pore diameter allows controlling the size of obtained titania particles. The TiO2/SBA-15 composites prepared by this study showed much higher photodegradation ability for methylene blue (MB) than commercial pure TiO2 nanoparticles P-25. Experimental results indicate that the photocatalytic activity of titania/silica mixed materials depends on the adsorption ability of composite and the photocatalytic activity of the titania, and there is an optimal ratio of Ti:Si, too high or low Ti:Si ratio will lower the photodegradation ability of the composites.     

Preparation and characterization of magnetically separable photocatalyst (TiO2/SiO2/Fe3O4): effect of carbon coating and calcination temperature

TiO2/SiO2/Fe3O4 composite was synthesized by sol-gel technique for silica and titania coatings on magnetite core to enable recovery after photocatalytic degradation. Carbon coating was also carried out by calcination of TiO2/SiO2/Fe3O4 under nitrogen atmosphere in presence of PVA as a source of carbon to enhance the adsorption of organic compounds on catalyst surface and to get better activity. All prepared samples were characterized using EDX, CN analyzer, XRD, BET and SEM. Degradation of methyl orange dye was used to assess the photocatalytic performance of the prepared samples. Calcination temperature was found to affect rate of reaction because of the formation of rutile phase at high calcination temperature. Carbon coated samples unexpectedly exhibited lower rate of reaction at almost all calcination temperatures.