Bi2MoO6纳米片/TiO2纳米棒阵列复合材料的制备及其可见光响应光电催化性能研究

Novel Bi₂MoO₆/TiO₂ heterojunction was fabricated by growing Bi₂MoO₆ nanosheets arrays on the vertically aligned TiO₂ nanorods arrays via a two-step solvothermal method. The obtained Bi₂MoO₆/TiO₂ hierarchical heterojunction showed excellent visible light photoelectrochemical performance. Compared with the pure TiO₂ and Bi₂MoO₆, the photocurrent density of the heterojunction was increased 57 and 29 times, respectively. Furthermore, the hydrogen generation rate of the Bi₂MoO₆/TiO₂ for photoelectrocatalytic water-splitting was about 6 times higher than that of the pure Bi₂MoO₆. The improved performance can be attributed to the synergistic effects of enhanced absorption of visible light, increase of migration rate and separation efficiency of photo-induced carriers.     

Preparation of visible light responsive N doped TiO2 via a reduction-nitridation procedure by nonthermal plasma treatment

A visible light responsive N-doped TiO₂ was prepared via a reduction-nitridation procedure by nonthermal plasma treatment. X-ray diffraction, N₂ adsorption, UV-vis spectroscopy, photoluminescence, and X-ray photoelectron spectroscopy were used to characterize the prepared TiO₂ samples. The plasma treatment did not change the phase composition and particle sizes of TiO₂ samples, but extended its absorption edges to the visible light region. The photocatalytic activities were tested in the degradation of an aqueous solution of a reactive dyestuff, methylene blue, under visible light. The photocatalytic activities of TiO₂ prepared by reduction-nitridation procedure were much higher than that of samples prepared by simple nitridation treatment. The enhanced activity was ascribed to the substitutional N-doping and appropriate concentration of oxygen vacancies. TOHN10 prepared by reduction-nitridation procedure exhibited excellent photocatalytic stability. A possible mechanism for the photocatalysis was proposed.     

Unusual photo-induced adsorption-desorption behavior of propylene on Ag/TiO2 nanotube under visible light irradiation

Titanium dioxide (TiO₂) nanotube with a large amount of single-electron-trapped-oxygen-vacancies (coded as T2) was obtained by annealing nanotube H₂Ti₂O₄(OH)₂ (coded as T1) at 400 °C in air. Silver nanoparticles with a diameter of about 30-50 nm were loaded onto the surface of T2 via deposition associated with photochemical reduction under ultraviolet irradiation. The resulting Ag/TiO₂ nanotube (coded as T3) was characterized by means of transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and ultraviolet-visible light diffusion reflectance spectrometry. It was found that C₃H₆ experienced unusual photo-induced adsorption-desorption on T3 under visible light irradiation. Namely, C₃H₆ was initially desorbed from T3 and then adsorbed on T3 under visible light irradiation. On the contrary, C₃H₆ was initially adsorbed on T3 in the dark, followed by desorption. The reason might lie in that two kinds of active sites exist on the surface of T3, corresponding to quite different rates of adsorption and desorption. It was found that oxygen vacancies in association with deposited silver particles, were responsible for the alternative adsorption-desorption of C₃H₆ on T3.     

Preparation and characterization of iodine-doped mesoporous TiO2 by hydrothermal method

Iodine-doped mesoporous TiO₂ (I/TiO₂) was prepared by hydrothermal method, using tetrabutyl titanate as precursor, potassium iodate as iodine sources. The as-prepared I/TiO₂ catalysts were characterized by UV-vis, XRD, TEM, BET, TG/DTA, XPS and photoluminescence (PL) spectroscopy. Production of OH radicals on the I/TiO₂ surface was detected by the PL technique using terephthalic acid as a probe molecule. The effects of hydrothermal reaction temperature, calcination temperature and iodine doping content on the structure and properties of the catalysts were investigated. The results showed that iodine-doped TiO₂ calcinated at 300 °C have good anatase crystal. The optimal hydrothermal conditions have been determined to be that reaction temperature 120 °C, calcinated temperature 300 °C and added 1.16 mmol iodine dopants. The average particle size of I/TiO₂ synthesized under optimal condition (I-3 sample) is about 3.9 nm. The I-3 photocatalyst contains 100% anatase crystalline phase of TiO₂. BET specific surface area of I-3 sample is184.8 m² g⁻¹ and is 3.67 times that of pure TiO₂ (50.37 m² g⁻¹). Iodine in I/TiO₂ catalyst mainly exists in the form of I₂, and photoactivity of I/TiO₂ catalyst in visible light comes from photosensitize of I₂. I/TiO₂ catalysis shows very high efficiency for the degradation of phenol under visible light.     

Enhanced visible light photocatalytic properties of Fe-doped TiO2 nanorod clusters and monodispersed nanoparticles

In order to get photocatalysts with desired morphologies and enhanced visible light responses, the Fe-doped TiO₂ nanorod clusters and monodispersed nanoparticles were prepared by modified hydrothermal and solvothermal method, respectively. The microstructures and morphologies of TiO₂ crystals can be controlled by restraining the hydrolytic reaction rates. The Fe-doped photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis absorption spectroscopy (UV-vis), N₂ adsorption-desorption measurement (BET), and photoluminescence spectroscopy (PL). The refinements of the microstructures and morphologies result in the enhancement of the specific surface areas. The Fe³⁺-dopants in TiO₂ lattices not only lead to the significantly extending of the optical responses from UV to visible region but also diminish the recombination rates of the electrons and holes. The photocatalytic activities were evaluated by photocatalytic decomposition of formaldehyde in air under visible light illumination. Compared with P25 (TiO₂) and N-doped TiO₂ nanoparticles, the Fe-doped photocatalysts show high photocatalytic activities under visible light.     

Photoelectrocatalytic degradation of organic contaminants at Bi2O3/TiO2 nanotube array electrode

In the current work, TiO₂ nanotube array was prepared via electrochemical anode method. Then the Bi₂O₃ nanoparticles were deposited onto the TiO₂ nanotube array via dip-coating method from an amorphous complex precursor. The crystal structures were characterized via X-ray diffraction analysis. Their surface textures were observed via electron-scanning microscope. The prepared composite array electrode exhibited high photoelectrocatalytic activities towards degrading organic contaminants under visible light irradiation. High photoelectrocatalytic activities were also exhibited under UV light irradiation. The catalytic mechanism was discussed based on the analysis of electrochemical and degradation kinetics results. It is suggested a P (Bi₂O₃)-N (TiO₂) junction was formed to increase the catalytic activates. The stability of the electrode materials was confirmed finally.     

Fabrication, characterization and photoelectrochemical properties of Fe2O3 modified TiO2 nanotube arrays

TiO₂ nanotube (NT) arrays modified by Fe₂O₃ with high sensibility in the visible spectrum were first prepared by annealing anodic titania NTs pre-loaded with Fe(OH)₃ which was uniformly clung to the titania NTs using sequential chemical bath deposition (S-CBD). The photoelectrochemical performances of the as-prepared composite nanotubes were determined by measuring the photo-generated currents and voltages under illumination of UV-vis light. The titania NTs modified by Fe₂O₃ showed higher photopotential and photocurrent values than those of unmodified titania NTs. The enhanced photoelectrochemical behaviors can be attributed to the modified Fe₂O₃ which increases the probability of charge-carrier separation and extends the range of the TiO₂ photoresponse from ultraviolet (UV) to visible region due to the low band gap of 2.2 eV of Fe₂O₃.     

Properties of carbon and iron modified TiO2 photocatalyst synthesized at low temperature and photodegradation of acid orange 7 under visible light

The nanoparticles of TiO₂ modified with carbon and iron were synthesized by sol-gel followed solvothermal method at low temperature. Its chemical composition and optical absorption were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence emission spectroscopy (PL), UV-vis absorption spectroscopy, and electron paramagnetic resonance (EPR). It was found that carbon and iron modification causes the absorption edge of TiO₂ to shift the visible light region. Fe(III) cation could be doped into the matrix of TiO₂, by which could hinder the recombination rate of excited electrons/holes. Superior photocatalytic activity of TiO₂ modified with carbon and iron was observed for the decomposition of acid orange 7 (AO7) under visible light irradiation. The synergistic effects of carbon and iron in modified TiO₂ nanoparticles were responsible for improving visible light photocatalytic activity.     

纤维状TiO2/Bi2O3光催化剂的制备及其光催化性能

以C₁₆H₃₆O₄Ti和Bi(NO₃)·5H₂O为原料,以棉花纤维为生物模板,合成了系列纤维状TiO₂/Bi₂O₃光催化剂．采用XRD、SEM、UV-Vis等测试技术对样品的相结构、形貌和吸光性能等进行了表征分析．结果表明,样品中的Bi₂O₃为单斜相和四方相共存的混晶,纤维长度达到毫米级,     

From anodic TiO2 nanotubes to hexagonally ordered TiO2 nanocolumns

We report on the formation of hexagonally ordered TiO₂ nanocolumnar layers by electrochemical oxidation in a fluoride containing electrolyte, using self-organizing nanotube formation conditions at elevated potentials and low temperatures. The influence of the substrate temperature on the nanocolumn morphology and composition is investigated and characterized by FE-SEM and EDX. The origin of these nanocolumns can be attributed to a thickening of the inner tube wall of the double wall structure of self-organized TiO₂ nanotubes. Furthermore, a transition from nanocolumnar to nanotubular structure can be established by changing the applied voltage or applying a post-immersion treatment.     

TiO2 activation using acid-treated vermiculite as a support: Characteristics and photoreactivity

Vermiculite was treated by sulfuric or nitric acid aqueous solutions with different concentration. These modified materials as the promising supports, were used to immobilize TiO₂. TiO₂ was prepared by the precursor, which was obtained by substituting partly isopropyl alcohol with Cl⁻ in titanium chloride {[Ti(IV)(OR)_nCl_m] (n = 2-3, m = 4 − n)}. The TiO₂/vermiculite composites were characterized by X-ray diffraction, scanning electron microscopy, and the nitrogen absorption. Their photocatalytic activity was evaluated by removal of methylene blue (MB). The pure anatase type crystalline phase was well deposited on the supports. The concentrations of acid for treatment had a significant influence on pore sizes and surface area of vermiculite. The treatment process changed microstructure of vermiculite, modified its characteristics, and farther improved the catalytic activity and absorption capacity of TiO₂/vermiculite composites. The treatment effect of nitric acid was superior to that of sulfuric acid.     

Photoelectrochemical property and photocatalytic activity of N-doped TiO2 nanotube arrays

N-doped TiO₂ nanotube arrays (NTN) were prepared by anodization and dip-calcination method. Hydrazine hydrate was used as nitrogen source. The surface morphology of samples was characterized by SEM. It showed that the mean size of inner diameter was 65 nm and wall thickness was 15 nm for NTN. The ordered TiO₂ nanotube arrays on Ti substrate can sustain the impact of doping process and post-heat treatment. The atomic ratio of N/Ti was 8/25, which was calculated by EDX. Photoelectrochemical property of NTN was examined by anodic photocurrent response. Results indicated the photocurrent of NTN was nearly twice as that of non-doped TiO₂ nanotube arrays (TN). Photocatalytic activity of NTN was investigated by degrading dye X-3B under visible light. As a result, 99% of X-3B was decomposed by NTN in 105 min, while that of TN was 59%.     

纤维状TiO2/BiVO4异质结的高可见光光催化性能

Novel TiO₂/BiVO₄ microfiber heterojunctions were constructed using cotton as biomorphic templates. The as-synthesized samples were characterized by scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectra and photocatalytic experiment. The morphology of the as-synthesized TiO₂/BiVO₄ composites was consisted of a large quantity of microfiber structures with diameter from 2.5 μm to 5 μm, and the surface of samples became more coarse and compact with the increase of weight ratio of TiO₂. The TiO₂/BiVO₄ samples with proper content (10.00wt%) showed the highest pho-tocatalytic degradation activity for methylene blue (MB) degradation among all the samples under visible light, and 88.58%MB could be degraded within 150 min. The enhancement of photocatalytic activity was mainly attributed to the formation of n-n heterojunction at the contact interface of TiO₂ and BiVO₄, which not only narrowed the band gap of BiVO₄ for extending the absorption range of visible light, but also promoted the transfer of charge carriers across interface. A possible photodegradation mechanism of MB in the presence of TiO₂/BiVO₄ microfibrous photocatalyst was proposed.     

Theoretical study of CO adsorption on the illuminated TiO2 (0 0 1) surface

A quantum modeling of the CO adsorption on illuminated anatase TiO₂ (0 0 1) is presented. The calculated adsorption energy and geometries of illuminated case are compared with the ground state case. The calculations were achieved by using DFT formalism and the BH and HLYP. Upon photoexcitation, an electron-hole pair is generated. Comparing of natural population in the ground state and the exited state, shows that an electron is trapped in a Ti⁴⁺ ion and a hole is localized in an oxygen ion. The photoelectron helps generation of a CO₂ molecule on the TiO₂ surface. As shown by optimization of these systems, the CO molecule adsorbed vertically on the TiO₂ (0 0 1) surface in the ground state case while the CO molecule made an angle of 134.3° to this surface at the excited state case. Based on the here used model the obtained adsorption energy was 0.36 eV which is in excellent agreement with the reported experimental value. In the present work the C-O stretch IR frequencies are calculated which are 1366.53 and 1423.16 cm⁻¹. These results are in good agreement with the earlier reported works for the surface carbonaceous compounds, and oxygenated carbon species.     

Surface effect of natural zeolite (clinoptilolite) on the photocatalytic activity of TiO2

The surface interaction between TiO₂ and natural zeolite, clinoptilolite, has been investigated by means of transmission electron microscope (TEM), atom force microscope (AFM), X-ray diffractometer (XRD), diffuse reflectance infrared Fourier transform (DRIFT) and far Fourier transform infrared ray (FTIR) spectroscopy. And the photocatalytic degradation (PCD) rate of methyl orange (MO), a model of recalcitrant azo dye, in aqueous system has been measured to compare the photocatalytic activities of different photocatalysts. A model has been carried out to explain the incorporation between TiO₂ particles and natural zeolite. The results show that the TiO₂ particles loaded on zeolite are 50 nm or so, smaller than the pure one, and combine with zeolite via chemical force. Since the reserved adsorption ability and the existence of electron trapper, the TiO₂-zeolite performed more efficient at low initial concentration and in the later period of PCD process, as compared with pure TiO₂ nanopowders.     

Synthesis of fluorinated TiO2 hollow microspheres and their photocatalytic activity under visible light

Fluorinated TiO₂ hollow microspheres with three-dimensional hierarchical architecture were prepared by solvothermally treatment using solid microspheres as precursor. The obtained solid and hollow TiO₂ microspheres were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectrum (DRS) and photoluminescence (PL) spectra. The photocatalytic activity of as-prepared solid and hollow TiO₂ microspheres was determined by degradation of methyl orange (MO) under visible light irradiation. The results showed that the surface fluorination, the existence of accessible mesopores channels, and the increased light harvesting abilities could remarkably improve the photocatalytic activity of TiO₂ hollow microspheres.     

Sputter deposition of high transparent TiO2−xNx/TiO2/ZnO layers on glass for development of photocatalytic self-cleaning application

In this study, TiO_2−xN_x/TiO₂ double layers thin film was deposited on ZnO (80 nm thickness)/soda-lime glass substrate by a dc reactive magnetron sputtering. The TiO₂ film was deposited under different total gas pressures of 1 Pa, 2 Pa, and 4 Pa with constant oxygen flow rate of 0.8 sccm. Then, the deposition was continued with various nitrogen flow rates of 0.4, 0.8, and 1.2 sccm in constant total gas pressure of 4 Pa. Post annealing was performed on as-deposited films at various annealing temperatures of 400, 500, and 600 °C in air atmosphere to achieve films crystallinity. The structure and morphology of deposited films were evaluated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). The chemical composition of top layer doped by nitrogen was evaluated by X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of samples was measured by degradation of Methylene Blue (MB) dye. The optical transmittance of the multilayer film was also measured using ultraviolet-visible light (UV-vis) spectrophotometer. The results showed that by nitrogen doping of a fraction (∼1/5) of TiO₂ film thickness, the optical transmittance of TiO_2−xN_x/TiO₂ film was compared with TiO₂ thin film. Deposited films showed also good photocatalytic and hydrophilicity activity at visible light.     

Preparation and characterization of amine-functionalized SiO2/TiO2 films for formaldehyde degradation

This paper investigated the gaseous formaldehyde degradation by the amine-functionalized SiO₂/TiO₂ photocatalytic films for improving indoor air quality. The films were synthesized via the co-condensation reaction of methyltrimethoxysilane (MTMOS) and 3-aminopropyltrimethoxysilane (APTMS). The physicochemical properties of prepared photocatalysts were characterized with N₂ adsorption/desorption isotherms measurement, X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FT/IR). The effect of amine-functional groups and the ratio of MTMOS/APTMS precursors on the formaldehyde adsorption and photocatalytic degradation were investigated. The results showed that the formaldehyde adsorption and photocatalytic degradation of the APTMS-functionalized SiO₂/TiO₂ film was higher than that of SiO₂/TiO₂ film due to the surface adsorption on amine sites and the relatively high of the specific surface area of the APTMS-functionalized SiO₂/TiO₂ film (15 times higher than SiO₂/TiO₂). The enhancement of the formaldehyde degradation of the film can be attributed to the synergetic effect of adsorption and subsequent photocatalytic decomposition. The repeatability of photocatalytic film was also tested and the degradation efficiency was 91.0% of initial efficiency after seven cycles.     

Cocktail effect of Fe2O3 and TiO2 semiconductors for a high performance dye-sensitized solar cell

The bi-semiconductors of TiO₂ and Fe₂O₃ were used as a photoelectrode material in a high performance dye-sensitized solar cell due to cocktail effects from the two conduction bands. The size of the semiconductors was reduced by using a paint shaker to enlarge the contact area of the semiconductor with the dye or electrolyte. The fill factor and the efficiency of the prepared dye-sensitized solar cell were improved by over 16% and 300%, respectively; these parameters were measured from a current-voltage curve that was based on the effects of the Fe₂O₃ co-semiconductor and the size reduction. A mechanism is suggested wherein the conduction band of Fe₂O₃ works to prohibit the trapping effects of electrons in the conduction band of TiO₂. This result is attributed to the prevention of electron recombination between electrons in the TiO₂ conduction band with dye or electrolytes. The mechanism is suggested based on impedance results, which indicate improved electron transport at the interface of the TiO₂/dye/electrolyte.     

Design and fabrication of a TiO2/nano-silicon composite visible light photocatalyst

Nano-silicon (nc-Si) was utilized as the charges generator to promote the photocatalytic and super-hydrophilic reactivity of TiO₂ film under visible light irradiation. The photocatalytic ability of TiO₂/nc-Si composite photocatalyst was evaluated by a set of experiments to photodecompose 100 ppm methylene blue (MB) in aqueous solution. And the super-hydrophilic property was characterized by measuring the water droplet contacts angle, under visible light irradiation in atmospheric air and at room temperature. Under 100 mW/cm² visible light irradiation, the droplet contact angles were reduced to 0° within 4 h with nc-Si charge generator. Additionally, the rate constant of MB photo-degradation was promoted 6.6 times.