Preparation and characterization of TiO2 photocatalysts co-doped with iron (III) and lanthanum for the degradation of organic pollutants

Titanium dioxide photocatalysts co-doped with iron (III) and lanthanum were prepared by a facile sol-gel method. The structure of catalysts was characterized by X-ray diffraction (XRD), Raman spectroscopy, UV-vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of the samples were evaluated by the degradation of methylene blue in aqueous solutions under visible light (λ > 420 nm) and UV light irradiation. Doping with Fe³⁺ results in a lower anatase to rutile (A-R) phase transformation temperature for TiO₂ particles, while doping with La³⁺ inhibits the A-R phase transformation, and co-doping samples indicate that Fe³⁺ partly counteracts the effect of La³⁺ on the A-R transformation property of TiO₂. Fe-TiO₂ has a long tail extending up the absorption edges to 600 nm, whereas La-TiO₂ results in a red shift of the absorption. However, Fe and La have synergistic effect in the absorption of TiO₂. Compared with Fe³⁺ and La³⁺ singly doped TiO₂, the co-doped simple exhibits excellent visible light and UV light activity and the synergistic effect of Fe³⁺ and La³⁺ is responsible for improving the photocatalytic activity.     

Visible-light-driven titania photocatalyst co-doped with nitrogen and ferrum

Nitrogen and ferrum co-doped titania photocatalyst was prepared by the sol-gel route. The prepared photocatalyst was characterized by various techniques including X-ray diffraction (XRD), UV-vis diffusive reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and N₂ adsorption-desorption isotherm. The photocatalytic activity of the co-doped titania photocatalyst was evaluated by the degradation of methyl orange (MO) from aqueous solution under visible light irradiation and was compared with that of the commercial TiO₂ photocatalyst (Degussa P25). The results revealed that the nitrogen doping could lead to the response to visible light and that the ferrum doping could improve the photocatalytic performance. The effects of the component and the annealing temperature of the co-doped titania photocatalyst on the photocatalytic activity were investigated.     

N,Fe, La三掺杂锐钛矿型TiO2能带调节的理论与实验研究

采用基于密度泛函理论(DFT)的平面波超软赝势方法(PWPP), 利用Material studio 计算N, Fe, La三种元素掺杂引起的锐钛矿TiO₂晶体结构、能带结构和态密度变化. 并通过溶胶-凝胶法制得锐钛矿型本征TiO₂, N, Fe共掺杂TiO₂和N, Fe, La共掺杂TiO₂; 用X射线衍射和扫描电镜表征结构; 紫外-可见分光光度计检测TiO₂对甲基橙的降解效率变化. 计算结果表明, 由于N, Fe, La三掺杂TiO₂的晶格体积、键长等发生变化, 导致晶体对称性下降, 光生电子-空穴对有效分离, 同时在导带底和价带顶形成杂质能级, TiO₂禁带宽度由1.78 eV变为1.35 eV, 减小25%, 光吸收带边红移, 态密度数增加, 电子跃迁概率提升, 光催化能力增加. 实验结果表明: 离子掺杂使颗粒变小, 粒径大小: 本征TiO₂>N/Fe_TiO₂>N/Fe/La_TiO₂, 并测得N/Fe/La_TiO₂发光峰425 nm, 能隙减小, 光催化能力比N/Fe_TiO₂强, 增强原因是杂质能级和电子态数量增加引起.     

Characterization and photocatalytic activity of Zn–TiO2/AC composite photocatalyst

Activated carbon (AC) supported Zn²⁺–TiO₂ photocatalyst was prepared by sol–gel method. The prepared samples were characterized by X-ray diffraction, scanning electron micrograph, nitrogen absorption, diffuse reflectance UV/VIS and X-ray photoelectron spectroscopy. Using toluene as a pollution target, the photocatalytic activity of photocatalyst was evaluated. The results showed that prepared photocatalyst was obviously helpful for the removal of toluene in air. The photocatalytic degradation of toluene by Zn²⁺–TiO₂/AC reached 100% for 40 min and remained 75% after 160 min, while degradation by TiO₂ was only 30%. It indicated that the photocatalytic activity of prepared photocatalyst was enhanced. It is due to Zn²⁺-doping increased the oxidation and reduction of hole–electron pairs, which was the important factor in heterogeneous photocatalysis.     

铁和镧共掺杂纳米二氧化钛光催化剂的制备、表征及其光催化活性

以葡聚糖为模板,钛酸四正丁酯、硝酸铁和硝酸镧为前驱体采用模板法制备了一系列铁、镧单掺杂及共掺杂纳米TiO₂光催化剂. 利用SEM、XRD、BET比表面积测定和UV-Vis等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征. 以甲基橙溶液的光催化降解为模型反应,考察了不同掺杂的样品在紫外和可见光下的光催化性能. TiO₂材料具有较大的比表面积(约150 m²/g),铁和镧共掺杂纳米TiO₂在可见光区域有较强的吸收,在紫外和可见光条件下较纯TiO₂和单掺杂TiO₂对甲基橙溶液具有更好的光催化降解效果,且铁和镧的掺杂量显著影响该材料的催化性能. 当铁掺杂量为0.5mol%、镧掺杂量为0.3mol%,在500 ℃焙烧2 h所得光催化材料的催化性能最佳,焙烧4 h即可使甲基橙的降解率达98.8%,且该复合材料有较高的循环回收利用率,重复使用4次仍可使甲基橙的降解率保持在88%以上.     

Ag2S nanoparticle encapsulated in mesoporous material nanoparticles and its application for photocatalytic degradation of dye in aqueous solution

Semiconductor loaded mesoporous materials in general possess greater photocatalytic activity than pure semiconductors. Hence, with an attempt to achieve higher photocatalytic activity, Ag₂S/MCM-41 photocatalysts were prepared by ion exchange method and used for the photocatalytic degradation of methylene blue. The materials were characterized by different analytical techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD), infrared spectroscopy (IR) and BET (Brunauer-Emmert-Teller) experiments. The effect of Ag₂S, MCM-41 support and different wt% of Ag₂S over the support on the photocatalytic degradation and influence of parameters such as Ag₂S loading, catalyst a mount, pH and initial concentration of dye on degradation are evaluated. The degradation reaction follows pseudo-first order kinetics. It was seen that 0.6 g/L of photocatalyst is an optimum value for the dosage of photocatalyst. The degradation efficiency was decreased in dye concentration above 3.2 ppm for dye.     

Influence of MoS2 deposition time on the photocatalytic activity of MoS2/ V,N co-doped TiO2 heterostructure thin film in the visible light region

Electron-hole separation and a narrow band-gap are essential steps to obtain efficient photocatalysis, towards which the use of co-catalysts or co-doped-TiO₂ photocatalysts has become a widely used strategy. In this article, the combination of MoS₂ and co-doping of V, N is the goal to achieve high performance photocatalysts. We synthesized MoS₂/V, N co-doped TiO₂ heterostructure thin film by sol-gel and chemical bath deposition methods. Herein, we investigated the influence of deposition time of MoS₂ layer on visible-photocatalytic activity of the obtained samples. The thin films were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and UV–vis spectroscopy techniques. Visible-photocatalytic activity of these samples were evaluated on the removal of methylene blue (MB) under visible light irradiation. The results show that the aforementioned heterostructure thin films have better photocatalytic activities than those of TiO₂, MoS₂ and V, N co-doped TiO₂ counterparts in visible light region. The mechanism for increasing visible-photocatalytic property of the heterostructure thin films is discussed in detail. We find that MoS₂/V, N co-doped TiO₂ heterostructure thin film at MoS₂ deposition time of 45-min shows the highest photocatalytic performance in the visible light region with MB photodegradation rate about 99% for 150 min and the degradation rate constant is 2.06 times higher than that of V and N co-doped TiO₂ counterpart.     

Gd, N-codoped trititanate nanotubes: Preparation, characterization and photocatalytic activity

Trititanate nanotubes were prepared using hydrothermal method and then co-doped with Gd³⁺ and N through ion-exchanging with H⁺. They were characterized by X-ray photoelectron spectra (XPS), high-resolution transmission electronmicroscopy (HRTEM), X-ray diffraction (XRD), UV-vis diffusion reflection spectra (UV-vis DRS) and photoluminescence (PL) spectra. The photocatalytic activities were investigated with Rhodamine B as the model pollutant. The results indicated that synergistic reaction occurred when codoping with Gd³⁺ and N and the photocatalytic activities of TiO₂ were enhanced significantly under visible light irradiation.     

Synthesis and characteristics of natural zeolite supported Fe-TiO2 photocatalysts

Natural zeolite supported Fe³⁺-TiO₂ photocatalysts were synthesized for the sake of improving the recovery and photocatalytic efficiency of TiO₂. The as-prepared materials were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflection spectroscopy (UV-vis DRS), scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX). Methyl orange was used to estimate the photocatalytic activity of the samples. The results showed that zeolite inhibited the growth of TiO₂ crystallite sizes. The Fe³⁺ concentration played an important role on the microstructure and photocatalytic activity of the samples. The iron ions could diffuse into TiO₂ lattice to the form Fe-O-Ti bond and gave TiO₂ the capacity to absorb light at lower energy levels. The photocatalytic activity of the samples could be enhanced as appropriate dosages of Fe³⁺ were doped.     

Visible-light-induced degradation of formaldehyde over titania photocatalyst co-doped with nitrogen and nickel

Titanium isopropoxide, ammonium carbonate and nickelous nitrate were used as the sources of titanium, nitrogen, and nickel to prepare titania photocatalyst co-doped with nitrogen and nickel by means of the modified sol-gel method. The photocatalyst was characterized by X-ray diffraction (XRD), UV-vis diffusive reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM). The prepared N-Ni co-doped photocatalyst showed optical absorption in the visible light area and exhibited excellent photocatalytic ability for the degradation of formaldehyde under visible light irradiation. The effects of annealing temperature and component on the phase composition and photocatalytic activity were investigated. The results demonstrated that nitrogen atoms was weaved into the structure of titania and led to the response to visible light. However, nickel atoms existed in the form of Ni₂O₃, dispersed on the surface of TiO₂, suppressed the recombination of photo-induced electron-hole pairs, raised the photo quantum efficiency, and led to the enhancement of photocatalytic performance. The increase of photoactivity was attributed to the synergistic effects of co-doping.     

Characterization and Photocatalytic Performance of Rb+-Doped TiO2 Photocatalysts

ABSTRACT

Rb⁺-doped TiO₂ nanoparticles with higher photocatalytic activity were prepared by sol–gel method. The prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive analysis of X-rays (EDAX), and surface area (BET) measurements. The photocatalytic activity for the degradation of rhodamine B (RhB) was evaluated. The effects of calcination temperature, Rb⁺-doping amount, and the dosage of catalyst in the reaction liquid were investigated. The results showed that Rb⁺ doping can inhibit phase transformation from anatase to rutile, increase surface area of TiO₂ crystals, and reduce crystallite size. TiO₂ doped with 1% Rb⁺ and calcined at 650°C shows much higher photoactivity than the others when the doping level of Rb⁺ and calcination temperature are 0–5% and 350–850°C, respectively. The kinetics of the degradation of RhB was also analyzed. The kinetics of this reaction fits the pseudo first-order kinetics model well, and the reaction rate constants for pure TiO₂ and Rb1-650 are 0.086 min^?1 and 0.226 min^?1 respectively. Doping with Rb⁺ improves the photocatalytic activity of TiO₂ significantly.     

Multiwalled carbon nanotubes decorated with nitrogen, palladium co-doped TiO2 (MWCNT/N, Pd co-doped TiO2) for visible light photocatalytic degradation of Eosin Yellow in water

Multiwalled carbon nanotube (MWCNT/N), Pd co-doped TiO₂ nanocomposites were prepared by calcining the hydrolysis products of the reaction of titanium isopropoxide, Ti(OC₃H₇)₄ containing multiwalled carbon nanotubes with aqueous ammonia. The prepared samples were characterised by Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetric analysis, diffuse reflectance UV?CVis spectrophotometry (DRUV?CVis), XRD, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). DRUV?CVis analysis confirmed the red shift in the absorption edge at lower MWCNT percentages. SEM and TEM images showed the complete coverage of the MWCNTs with clusters of anatase TiO₂ at low MWCNT percentages. Higher MWCNT levels led to their aggregation and consequently poor coverage by N, Pd co-doped TiO₂. The photocatalytic activities of the nanocomposites were monitored by photodegradation of Eosin Yellow under simulated solar and visible light irradiation (???>?450?nm). Irradiation with simulated solar radiation gave higher dye-degradation rates compared to visible radiation. The optimum MWCNT weight percentage in the composites was found to be 0.5. High degradation-rate constants of 3.42?×?10^?2 and 5.18?×?10^?3?min^?1 were realised for the 0.5% MWCNT/N, Pd co-doped TiO₂ composite, using simulated solar light and visible light, respectively.     

Synthesis, characterization and degradation of Bisphenol A using Pr, N co-doped TiO2 with highly visible light activity

Praseodymium and nitrogen co-doped titania (Pr/N-TiO₂) photocatalysts, which could degrade Bisphenol A (BPA) under visible light irradiation, were prepared by the modified sol-gel process. Tetrabutyl titanate, urea and praseodymium nitrate were used as the sources of titanium, nitrogen and praseodymium, respectively. The resulting materials were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), UV-vis absorbance spectroscopy, X-ray photoelectron spectroscopy (XPS), N₂ adsorption-desorption isotherm and Fourier transform infrared spectra (FTIR). It was found that Pr doping inhibited the growth of crystalline size and the transformation from anatase to rutile. The degradation of BPA under visible light illumination was taken as probe reaction to evaluate the photo-activity of the co-doped photocatalyst. In our experiments, the optimal dopant amount of Pr was 1.2 mol% and the calcination temperature was 500 °C for the best photocatalytic activity. Pr/N-TiO₂ samples exhibited enhanced visible-light photocatalytic activity compared to N-TiO₂, undoped TiO₂ and commercial P25. The nitrogen atoms were incorporated into the crystal of titania and could narrow the band gap energy. Pr doping could slow the radiative recombination of photogenerated electrons and holes in TiO₂. The improvement of photocatalytic activity was ascribed to the synergistic effects of nitrogen and Pr co-doping.     

Ultrasound assisted synthesis of doped TiO2 nano-particles: Characterization and comparison of effectiveness for photocatalytic oxidation of dyestuff effluent

The present work deals with the synthesis of titanium dioxide nanoparticles doped with Fe and Ce using sonochemical approach and its comparison with the conventional doping method. The prepared samples have been characterized using X-ray diffraction (XRD), FTIR, transmission electron microscopy (TEM) and UV–visible spectra (UV–vis). The effectiveness of the synthesized catalyst for the photocatalytic degradation of crystal violet dye has also been investigated considering crystal violet degradation as the model reaction. It has been observed that the catalysts prepared by sonochemical method exhibit higher photocatalytic activity as compared to the catalysts prepared by the conventional methods. Also the Ce-doped TiO₂ exhibits maximum photocatalytic activity followed by Fe-doped TiO₂ and the least activity was observed for only TiO₂. The presence of Fe and Ce in the TiO₂ structure results in a significant absorption shift towards the visible region. Detailed investigations on the degradation indicated that an optimal dosage with 0.8 mol% doping of Ce and 1.2 mol% doping of Fe in TiO₂ results in higher extents of degradation. Kinetic studies also established that the photocatalytic degradation followed the pseudo first-order reaction kinetics. Overall it has been established that ultrasound assisted synthesis of doped photocatalyst significantly enhances the photocatalytic activity.     

Effects of NiTiO3 nanoparticles supported by mesoporous MCM-41 on photoreduction of methylene blue under UV and visible light irradiation

In this work, we report the synthesis of nickel titanate nanoparticles loaded on nanomesoporous MCM-41 nanoparticles to determine the effect of MCM-41 nanoparticles on the photocatalytic activities of nickel titanate (NiTiO₃) nanoparticles by using simple solid-state dispersion (SSD) method. Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and UV–Vis diffuse reflectance spectra (DRS) analysis were used to characterize the size and morphology of the obtained nanocomposite. The photocatalytic activity (PA) of the as-prepared NiTiO₃ loaded on MCM-41 was evaluated by degradation of the methylene blue under irradiation of UV and visible light. The results showed that NiTiO₃ loaded on nanosize MCM-41 has higher photocatalytic activity than that of NiTiO₃ nanoparticles.     

Synthesis and application of the solar cell of poly(3-hexylthiophene)/Fe N/titanium dioxide nanocomposite material

A series of nanocomposites of poly(3-hexylthiophene) with Fe N-doped TiO₂ (P3HT/Fe N/TiO₂) were synthesized by the chemical method in situ. The structure of the prepared composites was characterized using X-ray diffraction patterns (XRD), infrared spectroscopy (IR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Optical and electrochemical properties were determined using UV-vis spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. These tests indicated that P3HT/Fe N/TiO₂ is a new p-n semiconductor. Two solar cells based on P3HT/Fe N/TiO₂ were manufactured and studied.     

Fabrication of Fe-doped TiO2 nanoparticles and investigation of photocatalytic decolorization of reactive red 198 under visible light irradiation

In this research, Fe-doped TiO₂ nanoparticles with various Fe concentrations (0. 0.1, 1, 5 and 10 wt%) were prepared by a sol–gel method. Then, nanoparticles were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis (EDX), BET surface area, photoluminescence (PL) spectroscopy and UV–vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the nano-particles was evaluated through degradation of reactive red 198 (RR 198) under UV and visible light irradiations. XRD results revealed that all samples contained only anatase phase. DRS showed that the Fe doping in the titania induced a significant red shift of the absorption edge and then the band gap energy decreased from 3 to 2.1 eV. Photocatalytic results indicated that TiO₂ had a highest photocatalytic decolorization of the RR 198 under UV irradiation whereas photocatalytic decolorization of the RR 198 under visible irradiation increased in the presence of Fe-doped TiO₂ nanoparticles. Among the samples, Fe-1 wt% doped TiO₂ nanoparticles showed the highest photocatalytic decolorization of RR198 under visible light irradiation.     

Effect of N2 ion flux on the photocatalysis of nitrogen-doped titanium oxide films by electron-beam evaporation

Nitrogen-doped titanium oxide (TiO_xN_y) films were prepared with ion-assisted electron-beam evaporation. The nitrogen (N) incorporated in the film is influenced by the N₂ flux modulated by the N₂ flow rate through an ion gun. The TiO_xN_y films have the absorption edge of TiO₂ red-shifted to 500 nm and exhibit visible light-induced photocatalytic properties in the surface hydrophilicity and the degradation of methylene blue. The structures and states of nitrogen in the films are investigated by X-ray diffraction patterns (XRD), and X-ray photoelectron spectroscopy (XPS) and related to their visible light-induced photocatalytic properties. The results indicate that the substitutional N in anatase TiO₂ can induce visible light photocatalysis. The substitutional N is readily doped by the energetic nitrogen ions from the ion gun. The best photocatalytic activity is obtained at the largest N loading about 5.6 at.%, corresponding to the most substitutional N in anatase TiO₂. The film exhibits the degradation of methylene blue with a rate-constant (k) about 0.065 h⁻¹ and retaining 7° water contact angle on the surface under visible light illumination.     

Preparation, characterization of Au (or Pt)-loaded titania nanotubes and their photocatalytic activities for degradation of methyl orange

TiO₂ nanotubes were prepared by hydrothermal method and Au (or Pt) was loaded on TiO₂ nanotubes by photodeposition method. The photocatalysts were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and N₂ adsorption technique, respectively. The photocatalytic properties of the samples were also investigated. The results show that TiO₂ nanotubes with uniform diameter were prepared, and they have specific surface areas over 400 m²/g. The specific surface areas of TiO₂ nanotubes decrease with the increasing of calcining temperature, and crystalline phase of TiO₂ in the wall of nanotubes was transformed from anatase into rutile phase in calcination process. The photocatalytic activities of TiO₂ nanotubes are higher than that of nanosized TiO₂, and the photocatalytic activities of TiO₂ nanotubes were enhanced after loading Au (or Pt). After irradiation for 40 min under a 300 W of middle-pressure mercury lamp (MPML), the degradation rate of methyl orange solution using the Au/TiNT-500 (or Pt/TiNT-500) as a catalyst can reach 96.1% (or 95.1%). On the other hand, Au-loaded sample has evident adsorption peak in visible range, indicating that Au-loaded TiO₂ nanotubes are hopeful to become visible light photocatalyst.     

Graphene-based hollow TiO2 composites with enhanced photocatalytic activity for removal of pollutants

Catalytically active graphene-based hollow TiO₂ composites(TiO₂/RGO) were successfully synthesized via the solvothermal method. Hollow TiO₂ microspheres are uniformly dispersed on RGO. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) were used for the characterization of prepared photocatalysts. The mass of GO was optimized in the photocatalytic removal of rhodamine B (RhB) as a model dye pollutants. The results showed that graphene-based hollow TiO₂ composites exhibit a significantly enhanced photocatalytic activity in degradation of RhB under either UV or visible light irradiation. The formation of the graphene-based hollow TiO₂ composites and the photocatalytic mechanisms under UV and visible light were also discussed.