硼铈共掺杂纳米TiO2光催化降解三氯杀螨醇和菊酯类农药

采用溶胶-凝胶法在钛酸丁酯水解过程引入硼酸、硝酸铈,制备具有光催化活性的硼铈共掺杂纳米二氧化钛（TiO2）,经XRD、TEM、FT-IR、UV-Vis-DRS表征晶体结构,在日光灯照射下,光催化降解三氯杀螨醇、高氟氯氰菊酯、氟戊菊酯农药。结果表明：硼铈共掺杂的TiO2只有锐钛矿型,而纯的或掺铈的TiO2有含有锐钛矿型、金红石相和少量板钛矿型,UV-Vis-DRS测定结果表明硼铈共掺杂的TiO2禁带宽度变小,硼铈共掺杂的TiO2在可见光区吸光度高于掺杂铈和不掺杂的TiO2,在420nm~850nm有强的吸收;在同样光照下对三氯杀螨醇、高氟氯氰菊酯、氟戊菊酯的降解试验证明硼铈共掺杂纳米TiO2的光催化活性高于不掺杂或只掺杂铈的TiO2。     

Photo Catalytic Degradation of Azo Dyes over Mn2+ Doped TiO2 Catalyst under UV/Solar Light:An Insight to the Route of Electron Transfer in the Mixed Phase of Anatase and Rutile

Mn²⁺ ion was doped into the TiO₂ matrix and its photocatalytic activity was evaluated for the degradation of a mono azo dye methyl orange (MO) and a di‐azo dye brilliant yellow (BY) under UV/solar light. X‐ray diffraction results revealed the phase transformation from anatase to rutile due to the inclusion of Mn²⁺ ion into the TiO₂ matrix. All the doped catalysts showed a red shift in the band gap to the visible region. The degradation reaction of the dyes was found to be dependent on its structure. It was found that mono azo dye degrades faster than di azo dye under UV/solar light. The rate constant under identical conditions calculated for the degradation of MO is 2.4 times (under UV light) and 4.5 times (under solar light) higher compared to BY. Among the photocatalysts studied, Mn²⁺(0.06 at.%)‐TiO₂ showed higher activity under both UV and solar light illumination. The synergestic effect in the bicrystalline framework of anatase and rutile effectively suppresses the charge carrier recombination and enhances the photocatalytic activity. The degradation reaction was followed by UV‐visible spectroscopy and the photoproducts formed were analyzed by GC‐MS techniques.     

Photodegradation of Rhodamine B on Sulfur Doped ZnO/TiO2 Nanocomposite Photocatalyst under Visible-light Irradiation

Sulfur doped ZnO/TiO₂ nanocomposite photocatalysts were synthesized by a facile sol‐gel method. The structure and properties of catalysts were characterized by X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), UV‐vis diffusive reflectance spectroscopy (DRS) and N₂ desorption‐adsorption isotherm. The XRD study showed that TiO₂ was anatase phase and there was no obvious difference in crystal composition of various S‐ZnO/TiO₂. The XPS study showed that the Zn element exists as ZnO and S atoms form SO^2?₄. The prepared samples had mesoporosity revealed by N₂ desorption‐adsorption isotherm result. The degradation of Rhodamine B dye under visible light irradiation was chosen as probe reaction to evaluate the photocatalytic activity of the ZnO/TiO₂ nanocomposite. The commercial TiO₂ photocatalyst (Degussa P25) was taken as standard photocatalyst to contrast the prepared different photocatalyst in current work. The improvement of the photocatalytic activity of S‐ZnO/TiO₂ composite photocatalyst can be attributed to the suitable energetic positions between ZnO and TiO₂, the acidity site caused by sulfur doping and the enlargement of the specific area. S‐3.0ZnO/TiO₂ exhibited the highest photocatalytic activity under visible light irradiation after Zn amount was optimized, which was 2.6 times higher than P25.     

Sulfur and Ti3+ co‐Doping of TiO2 Nanotubes Enhance Photocatalytic H2 Evolution Without the Use of Any co‐catalyst

TiO₂ nanotubes were successfully co‐doped with sulfur and Ti³⁺ states using a facile annealing treatment in H₂/H₂S gas mixture. The obtained nanotubes were investigated for their photocatalytic performance and characterized by SEM, XRD, XPS, EPR, IPCE, IMPS and Mott‐Schottky measurements. The synthesized co‐doped TiO₂ nanotubes show an enhanced photocatalytic hydrogen production rate compared to tubes that were treated only in pure H₂ or H₂S atmosphere—this without the presence of any co‐catalyst. It was found that sulfur in co‐doped TiO₂ exists in the form of S^2? and a small quantity of S⁴⁺/S⁶⁺, which leads to a narrowing of the band gap. However, the enhanced absorption of light in the visible range is not the key reason for the improved photocatalytic performance. We ascribe the enhanced photocatalytic activity to a synergetic effect of S mid‐gap states and disordered Ti³⁺ defects that facilitate photo generated electron transfer.     

Effect of Erbium on the Photocatalytic Activity of TiO2/Ag Nanocomposites under Visible Light Irradiation

Erbium co‐doped TiO₂/Ag catalysts are synthesized by using a simple, one‐step solvothermal method and characterized by X‐ray diffraction, field‐emission scanning electron microscopy, transmission electron microscopy, Raman analysis, X‐ray photoelectron spectroscopy, and diffuse reflectance spectroscopy. The catalysts exhibit anatase crystal structures with increased visible light absorption compared with pure TiO₂. Enhanced photocatalytic activity is observed with Er co‐doped TiO₂/Ag nanocomposites for Rhodamine B degradation under visible light irradiation. The photocatalytic activity of 1 % Er co‐doped TiO₂/Ag is much higher than that of TiO₂/Ag, TiO₂/Er, pure TiO₂, and commercial Degussa P25. The kinetics of the degradation process are studied and the pseudo‐first‐order rate constant (k) and half‐life time (t_1/2) of the reaction are calculated. The enhanced activity might be accredited to the efficient separation of electron–hole pairs by silver and higher visible light absorption of TiO₂ induced by Er.     

Preparation of Cr‐doped TiO2/SiO2 Photocatalysts and their Photocatalytic Properties

Cr‐doped TiO₂/SiO₂ nanostructured materials were prepared employing a layer‐by‐layer assemblym technique. TiO₂ colloids were synthesized by a sol‐gel method using TiCl₄ as a precursor. The experimental results showed that sphere‐type TiO₂ particles on SiO₂ exhibited uniform shape and a narrow size distribution. The amount of Ti (wt %) increased as a function of the number of the coating layers. The coatingv layers was composed of anatase titania nanocrystals at 550 °C. The onset of band‐gap transition for Crdoped TiO₂/SiO₂ showed a red shift compared with that for the undoped TiO₂/SiO₂. And the photocatalytic activity of Cr‐doped TiO₂/SiO₂ was higher than that of undoped sample.     

Photocatalytic activity of polyaniline/Fe-doped TiO2 composites by in situ polymerization method

This study was focused on the photocatalytic activity of polyaniline (Pani)/iron doped titanium dioxide (Fe–TiO₂) composites for the degradation of methylene blue as a model dye. TiO₂ nanoparticles were doped with iron ions (Fe) using the wet impregnation method and the doped nanoparticles were further combined with Pani via an in situ polymerization method. For comparison purposes, Pani composites were also synthesized in the presence undoped TiO₂. The photocatalyst and the composites were characterized by standard analytical techniques such as FTIR, XRD, SEM, EDX and UV–Vis spectroscopies. Fe–TiO₂ and its composites exhibited enhanced photocatalytic activity under ultraviolet light irradiation. Improved photocatalytic activity of Fe–TiO₂ was attributed to the dopant Fe ions hindering the recombination of the photoinduced charge carriers. Pani/Fe–TiO₂ composite with 30?wt.% of TiO₂ nanoparticles achieved 28% dye removal and the discoloration rate of methylene blue for the sample was 0.0025?min^?1. FTIR, XRD, SEM, EDX and UV–Vis spectroscopies supported the idea that Fe ions integrated into TiO₂ crystal structure and Pani composites were successfully synthesized in the presence of the photocatalyst nanoparticles. The novelty of this study was to investigate the photocatalytic activity of Pani composites, containing iron doped TiO₂ and to compare their results with that of Pani/TiO₂.     

Tungsten and nitrogen co‐doped TiO2 nanobelts with significant visible light photoactivity

Tungsten and nitrogen co‐doped TiO₂ nanobelts (W/N‐TNBs) have been successfully synthesized via 1‐step hydrothermal method. The structure, morphology, and composition of prepared samples were characterized by X‐ray diffraction, scanning electron microscopy, and X‐ray photoelectron spectroscopy, respectively. The prominent phase of all as‐prepared samples is anatase crystal. For samples with N doping, new energy states can be introduced on top of O 2p states which reduced the band gap by 1.1 eV. The reduced band gap leads to efficient visible light activity. The 3%‐W/N‐TNBs were found to exhibit the highest activity. The photocatalytic performance of 3%‐W/N‐TNBs under visible light is about 4.8 times than that of pure TiO₂ nanobelts, which emphasizes the synergistic effect of W and N co‐doping for effectively inhibiting the recombination of photogenerated electrons and holes. In addition, our results testify the different redox potentials of the photoelectrons at different final states.     

Synthesis and Modification of Zn‐doped TiO2 Nanoparticles for the Photocatalytic Degradation of Tetracycline

The synthesis of Zn‐doped TiO₂ nanoparticles by solgel method was investigated in this study, as well as its modification by H₂O₂. The catalyst was characterized by transmission electron microscopy, X‐ray diffraction, Brunauer–Emmett–Teller, UV–visible reflectance spectra and X‐ray photoelectron spectroscopy (XPS). The results indicated that doping Zn into TiO₂ nanoparticles could inhibit the transformation from anatase phase to rutile phase. Zn existed as the second valence oxidation state in the Zn‐doped TiO₂. Zn‐doped TiO₂ that was synthesized by 5% Zn doping at 450°C exhibited the best photocatalytic activity. Then, the H₂O₂ modification further enhanced the photocatalytic activity. Zn doping and H₂O₂ modifying narrowed the band gap and efficiently increased the optical absorption in visible region. The optimal degradation rate of tetracycline by Zn‐doped TiO₂ and H₂O₂ modified Zn‐doped TiO₂ was 85.27% and 88.14%. Peroxide groups were detected in XPS analysis of H₂O₂ modified Zn‐doped TiO₂, favoring the adsorption of visible light. Furthermore, Zn‐doped TiO₂ modified by H₂O₂ had relatively good reusability, exhibiting a potential practical application for tetracycline's photocatalytic degradation.     

Preparation of TiO<Subscript>2</Subscript> nanofibers immobilized on quartz substrate by electrospinning for photocatalytic degradation of ranitidine

The photocatalytic activity of TiO₂ nanofibers immobilized on quartz substrates was investigated by evaluating the decomposition of organic pollutants. TiO₂ nanofibers were synthesized by electrospinning the Ti-precursor/polymer mixture solution, followed by hot-pressing for enhancing the adhesion of TiO₂-nanofiber films to the substrates. TiO₂ started to crystalize in the anatase form at 500 °C and reached the optimal photocatalytic anatase/rutile phase ratio of 70:30 at a calcination temperature of 600 °C. The TiO₂-nanofiber film was demonstrated to be an efficient photocatalyst by ranitidine decomposition under UV illumination and was proven to have a comparable photocatalytic activity with the well-known Degussa P25 nanoparticulate photocatalyst and excellent recyclability during 10 cycles of photocatalytic operation, indicating no loss of TiO₂ nanofibers during photocatalytic operations.     

The Influence of Defects on Mo‐Doped TiO2 by First‐Principles Studies

TiO₂ doped with transition metals shows improved photocatalytic efficiency. Herein the electronic and optical properties of Mo‐doped TiO₂ with defects are investigated by DFT calculations. For both rutile and anatase phases of TiO₂, the bandgap decreases continuously with increasing Mo doping level. The 4d electrons of Mo introduce localized states into the forbidden band of TiO₂, and this shifts the absorption edge into the visible‐light region and enhances the photocatalytic activity. Since defects are universally distributed in TiO₂ or doped TiO₂, the effect of oxygen deficiency due to oxygen vacancies or interstitial Mo atoms is systemically studied. Oxygen vacancies associated with the Mo dopant atoms or interstitial Mo will reduce the spin polarization and magnetic moment of Mo‐doped TiO₂. Moreover, oxygen deficiency has a negative impact on the improved photocatalytic activity of Mo‐doped TiO₂. The current results indicate that substitutional Mo, interstitial Mo, and oxygen vacancy have different impacts on the electronic/optical properties of TiO₂ and are suited to different applications.     

High temperature stability and photocatalytic activity of nanocrystalline anatase powders with Zr and Si co-dopants

TiO₂ nanopowders doped by Si and Zr were prepared by sol–gel method. The effects of Si and Zr doping on the structural, optical, and photo-catalytic properties of titania nanopowders have been studied by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and UV–Vis absorption spectroscopy. XRD results suggest that adding impurities has a significant effect on anatase phase stability, crystallinity, and particle size of TiO₂. Titania rutile phase formation in ternary system (Ti–Si–Zr) was inhibited by Zr⁴⁺ and Si⁴⁺ co-doped TiO₂ in high temperatures (500–900 °C) and 36 mol% anatase composition is retained even after calcination at 1,000 °C. The photocatalyst activity was evaluated by photocatalytic degradation kinetics of aqueous methylen orange under visible radiation. The results show that the photocatalytic activity of the 20 %Si and 15 %Zr co-doped TiO₂ nanopowders have a larger degradation efficiency than pure TiO₂ under visible light.     

Preparation and characterization of nitrogen-doped TiO2 photocatalyst in different acid environments

Nitrogen-doped TiO₂ powders were successfully prepared by a wet method, i.e., a micro-emulsion-hydrothermal method, in different acid environments. Several characterization techniques, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-visible diffuse reflectance spectra, were combined to determine the crystal phase, concentration and chemical states of the nitrogen doped in TiO₂. The high photocatalytic activity of the nitrogen-doped TiO₂ was evaluated through the decomposition of rhodanmine B under visible light irradiation. It was suggested that the doped nitrogen formed oxynitride (NO) and produced impurity states at higher above the valence band of TiO₂. Therefore, the nitrogen doping could enhance the response of photocatalyst to the visible light and improve the photocatalytic activity because of the narrowing of band gap of TiO₂.     

Characterization and photocatalytic activity of Fe- and N-co-deposited TiO2 and first-principles study for electronic structure

Titanium dioxide (TiO₂), co-deposited with Fe and N, is first implanted with Fe by a metal plasma ion implantation (MPII) process and then annealed in N₂ atmosphere at a temperature regime of 400-600 °C. First-principle calculations show that the (Fe, N) co-deposited TiO₂ films produced additional band gap levels at the bottom of the conduction band (CB) and on the top of the valence band (VB). The (Fe, N) co-deposited TiO₂ films were effective in both prohibiting electron-hole recombination and generating additional Fe-O and N-Ti-O impurity levels for the TiO₂ band gap. The (Fe, N) co-deposited TiO₂ has a narrower band gap of 1.97 eV than Fe-implanted TiO₂ (3.14 eV) and N-doped TiO₂ (2.16 eV). A significant reduction of TiO₂ band gap energy from 3.22 to 1.97 eV was achieved, which resulted in the extension of photocatalytic activity of TiO₂ from UV to Vis regime. The photocatalytic activity and removal rate were approximately two-fold higher than that of the Fe-implanted TiO₂ under visible light irradiation.     

Preparation,characterization and enhanced photocatalytic activity of Ni<Superscript>2+</Superscript> doped titania under solar light

Anatase TiO₂ was prepared by sol-gel method through the hydrolysis of TiCl₄. Ni²⁺ was doped into the TiO₂ matrix in the concentration range of 0.02 to 0.1 at.% and characterized by various analytical techniques. Powder X-ray diffraction revealed only anatase phase for all the samples, while diffuse reflectance spectral studies indicated a red shift in the band gap absorption to the visible region. The photocatalytic activities of these photocatalysts were probed for the degradation of methyl orange under natural solar light. The photocatalyst with optimum doping of 0.08 at.% Ni²⁺, showed enhanced activity, which is attributed to: (i) effective separation of charge carriers and (ii) large red shift in the band gap to visible region. The influence of crystallite size and dopant concentration on the charge carrier trapping — recombination dynamics is investigated.     

Visible-light-driven boron/ferrum/cerium/titania photocatalyst

A boron/ferrum/cerium/titania photocatalyst with visible-light-induced performance was prepared by the conventional sol–gel method, in which tetrabutyl titanate (Ti(O-nC₄H₉)₄) was used as the precursor and boric acid (H₃BO₃), ferric nitrate enneahydrate (Fe(NO₃)₃·9H₂O), and cerium nitrate hexahydrate (Ce(NO₃)₃·6H₂O) were the sources of boron, ferrum, and cerium, respectively. The microstructure and optical property of the photocatalyst were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), N₂ adsorption–desorption isotherm, and UV–vis diffusive reflectance spectroscopy (DRS). It was found that the as-prepared photocatalyst composed of anatase and that the presence of impurities could retard phase transformation of TiO₂ from anatase to rutile at elevated temperatures and could prohibit growth of polycrystalline, which favored forming photocatalyst with large surface area. Degradation of 2,4-dichlorophenol (DCP) under visible light illumination was used to evaluate the photocatalytic activity. Comparative investigations showed that photocatalytic performance of the boron/ferrum/cerium/titania photocatalyst was the highest among the all test samples. It was testified that boron doping led to the band gap narrow and the response to visible light, and that ferrum and cerium impurities, which presented in the forms of FeO/Fe₂O₃ and Ce₂O₃/CeO₂, dispersed on the surface of TiO₂, suppressed the electron and hole recombination, and resulted in the enhancement of catalytic performance. The results exhibited that the synergistic effects of boron, ferrum and cerium played an important role in the band gap narrow and the increase of photoactivity.     

Synthesis of W‐doped TiO2 by low‐temperature hydrolysis: Effects of annealing temperature and doping content on the surface microstructure and photocatalytic activity

A series of tungsten‐doped Titania photocatalysts were synthesized using a low‐temperature method. The effects of dopant concentration and annealing temperature on the phase transitions, crystallinity, electronic, optical, and photocatalytic properties of the resulting material were studied. The X‐ray patterns revealed that the doping delays the transition of anatase to rutile to a high temperature. A new phase W_yTi_1‐yO₂ appeared for 5.00 wt% W‐TiO₂ annealed at 900 °C. Raman and diffuse reflectance UV–Vis spectroscopy showed that band gap values decreased slightly up to 700 °C. X‐ray photoelectron spectroscopy showed that surface species viz. Ti³⁺, Ti⁴⁺, O^2?, oxygen‐vacancies, and adsorbed OH groups vary depending on the preparation conditions. The photocatalytic activity was evaluated via the degradation of methylene blue using LED white light. The degradation rate was affected by the percentage of dopants. The best photocatalytic activity was achieved with the sample labeled 5.00 wt% W‐TiO₂ annealed at 700 °C.     

Fe3+掺杂TiO2/凹凸棒复合光催化剂的制备和光催化活性

用酸催化溶胶-凝胶法制备了Fe³⁺掺杂TiO₂/凹凸棒（Fe³⁺-TiO₂/ATP）复合光催化剂,对其结构、微观形貌、光吸收性能和可见光下的光催化性能进行了表征。XRD和TEM测试结果表明,Fe³⁺-TiO₂/ATP具有较好的热稳定性,经450 ℃热处理后的ATP晶体结构基本保持不变,锐钛矿TiO2均匀的分布在ATP表面,TiO2颗粒之间无团聚,且平均粒径小于纯TiO₂。UV-Vis-DRS测试结果表明,Fe³⁺的掺杂可明显增强复合光催化剂对可见光的吸收,光响应范围拓展到了整个紫外-可见光区。在可见光下,Fe³⁺-TiO₂/ATP复合光催化剂对亚甲基蓝具有很好的催化降解活性。Fe³⁺-TiO₂/ATP的反应速率常数分别为TiO₂/ATP、P25和纯TiO2的1.37、4.83和6.51倍。复合光催化剂的沉降性能优于纯TiO2和P25,易于分离。     

Optimizing electronic structure and charge transport of sulfur/potassium co‐doped graphitic carbon nitride with efficient photocatalytic hydrogen evolution performance

Recently, graphitic carbon nitride (CN) has been widely investigated for solar energy conversion through water splitting, but its low photocatalytic activity needs to be further improved and optimized. Herein, S/K co‐doped CN photocatalysts have been fabricated by condensation of thiourea and dithiooxamide followed by post‐treatment in molten salt. As evidenced by XRD patterns and UV–vis DRS plots, the engineering crystalline and electronic structure of all as‐prepared samples have been explored through tailoring the mass ratio of thiourea and dithiooxamide as well as ratio of molten salt/the precursor. After optimization, the as‐prepared S/K co‐doped CN photocatalysts with needle‐like nanorods structure exhibit excellent hydrogen evolution rate of 1962.10 μmol^?1 g^?1 h^?1. While its photocatalytic activity is lower than that of pure CN by molten salt treatment (K‐doped CN) (2066.40 μmol^?1 g^?1 h^?1), which results from that the K content of S/K co‐doped CN photocatalyst is lower than that of K‐doped CN. Moreover, compared with K‐doped CN, S/K co‐doped CN photocatalyst possesses higher photocatalytic performance when irradiated by a light source (λ > 520 nm). This might be ascribed to the fact that the introduction of sulfur can expand light absorption region (λ > 520 nm), whereas K cannot improve light absorption of CN in this wavelength region. Furthermore, DFT calculation reveals that both S and K atoms can offer more electrons to band gap, leading to the formation of metallic‐character band structure. In addition, K atom can intercalate in the interlayer of CN and bridge the adjacent two layers, leading to the formation of charge delivery channels. These results demonstrate that S/K co‐doped CN photocatalysts facilitate the separation and transport of photogenerated charge carries, resulting in the efficient photocatalytic activity for hydrogen evolution. Besides, a competition between sulfur and potassium atom during the synthesis process is also discussed in details.     

Sonophotocatalytic activity of methyl orange over Fe(III)/TiO2

TiO₂ doped with Fe³⁺ was prepared by an impregnation technique and its sonophotocatalytic activity over methyl orange (MO) was investigated. The Fe/TiO₂ surface presented red shift to longer wavelength, resulting in a lower energy band gap. Fe loading of 0.1 wt% on TiO₂ provided the optimum degradation. The MO degradation rate constant under sonophotocatalytic conditions was 2.5 times higher than under photocatalytic conditions.