Structural,optical and photocatalytic activity of cerium doped zinc aluminate

Zinc aluminate and cerium-doped zinc aluminate nanoparticles are synthesised by co-precipitation method. Ammonium hydroxide is used as a precipitating agent. The synthesised compounds are characterised by powder X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FT-IR), Ultraviolet diffuse reflectance spectroscopy (UV-DRS), Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM) and Surface area measurements. The photocatalytic activity of zinc aluminate and cerium doped zinc aluminate nanoparticles are studied under the UV light and visible light taking methylene blue as a model pollutant. The amount of catalyst, concentration of dye solution and time are optimised under UV-light. Degradation of methylene blue under the UV-light is found to be 99% in 20 min with 10 mg of cerium doped catalyst. Compared to visible light degradation, the degradation of dye under UV-light is higher. Cerium doping in zinc aluminate (ZnAl₂O₄:Ce³⁺) increased the photocatalytic activity of zinc aluminate.     

Photocatalytic oxidation of organic dyes with visible-light-driven codoped TiO2 photocatalysts

A novel copper (II) and zinc (II) codoped TiO₂ photocatalyst was synthesized by a modified sol-gel method using titanium (IV) isopropoxide, Zn(NO₃)₂ · 6H₂O and copper(Il) nitrate as precursors. The samples were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS) and photo-luminescence spectra (PL). The XRD results showed undoped and Zn, Cu-codoped TiO₂ nanoparticles mainly including anatase phase and a tiny amount of Zn- and Cu-oxides exist in the mixed system, which is attributed to the decomposition of copper and zinc nitrates in the TiO₂ gel to form CuO and ZnO and randomly dispersed on the TiO₂ surface. On the basis of the optical characterization results, we found that the codoping of copper (II) and zinc (II) resulted a red shift of adsorption and lower recombination probability between electrons and holes, which were the reasons for high photocatalytic activity of Zn, Cu-codoped TiO₂ nanoparticles under visible light (λ > 400 nm). The photocatalytic activity of samples was tested for degradation of methyl orange (MO) in solutions. The results indicated that the visible-light driven capability of the codoped catalyst were much higher than that of the pure TiO₂ catalyst under visible irradiation. Because of the synergetic effect of copper (II) and zinc (II) element, the Zn, Cu-codoped TiO₂ catalyst will show higher quantum yield and enhance absorption of visible light. In the end, a key mechanism was proposed in order to account for the enhanced activity.     

Sol-gel preparation and characterization of Co/TiO<Subscript>2</Subscript> nanoparticles: Application to the degradation of methyl orange

Cobalt doped titania nanoparticles were synthesized by sol-gel method using titanium(IV) isopropoxide and cobalt nitrate as precursors. X-Ray diffraction (XRD) results showed that titania and Co/TiO₂ nanoparticles only include anatase phase. The framework substitution of Co in TiO₂ nanoparticles was established by XRD, scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX) and Fourier transform infrared (FT-IR) techniques. Transmission electron microscopy (TEM) images confirmed the nanocrystalline nature of Co/TiO₂. The increase of cobalt doping enhanced “red-shift” in the UV-Vis absorption spectra. The dopant suppresses the growth of TiO₂ grains, agglomerates them and shifts the band absorption of TiO₂ from ultraviolet (UV) to visible region. The photocatalytic activity of samples was tested for degradation of methyl orange (MO) solutions. Although the photocatalytic activity of undoped TiO₂ was found to be higher than that of Co/TiO₂ under UV irradiation, the presence of 0.5% Co dopant in TiO₂ resulted in a catalyst with the highest activity under visible irradiation.     

Transition metals Fe3+, Ni2+ modified titanium dioxide (TiO2) film sensors fabricated by CPT method to sense some toxic environmental pollutant gases

The present investigation deals synthesis of undoped TiO₂, Ni²⁺ doped TiO₂, and Fe³⁺ doped TiO₂ nanoparticles by low-cost co-precipitation (CPT) method. The thick film sensors of all the fabricated modified TiO₂ nanoparticles were designed by a screen printing strategy. The prepared thick film sensors were characterized by various sophisticated techniques. The structural parameters of undoped TiO₂ and modified TiO₂ film sensors were characterized by X-Ray Diffraction (XRD) which confirmed anatase phase of TiO₂ lattice. The surface morphological properties of all the prepared materials were confirmed by means of scanning electron microscope (SEM). The energy dispersive spectroscopy (EDS) confirms the elemental composition of all the prepared materials. High-Resolution Transmission Electron Microscopy (HR-TEM) was utilized to investigate the crystal lattice of fabricated TiO₂ material. The HR-TEM results revealed the anatase phase crystal morphology of prepared material. The prepared TiO₂ materials were also characterized by means of X-Ray photoelectron spectroscopy (XPS) to confirm the surface doping, specific biding energies, chemical states and elemental composition of modified TiO₂ materials. The Brunauer–Emmett–Teller (BET) study was carried to investigate the specific surface area of all the prepared sensors. The Fe³⁺ doped TiO₂ sensor found with enhanced surface area (83.10 ​m²/g) in comparison to Ni²⁺ doped TiO₂ and bare TiO₂ (67.34 ​m²/g). All the prepared materials were investigated for gas sensing characteristics. The NO₂, SO₂, and CO₂ gases were investigated for all the prepared sensors. The reusability test confirms that the Fe³⁺ doped TiO₂ is reproducible and stable sensor for long time repeated sensing of SO₂ and NO₂ vapors. Importantly, Fe³⁺ doped TiO₂ sensor showed rapid response and recovery towards SO₂ and NO₂ vapors.     

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.     

Photocatalytic activity of nitrogen and copper doped TiO2 nanoparticles prepared by microwave-assisted sol-gel process

Cu and N-doped TiO₂ photocatalysts were synthesized from titanium (IV) isopropoxide via a microwave-assisted sol-gel method. The synthesized materials were characterized by X-ray diffraction, UV-vis diffuse reflectance, photoluminescence (PL) spectroscopy, SEM, TEM, FT-IR, Raman spectroscopy, photocurrent measurement technique, and nitrogen adsorption–desorption isotherms. Raman spectra and XRD showed an anatase phase structure. The SEM and TEM images revealed the formation of an almost spheroid mono disperse TiO₂ with particle sizes in the range of 9-17 nm. Analysis of N₂ isotherm measurements showed that all investigated TiO₂ samples have mesoporous structures with high surface areas. The optical absorption edge for the doped TiO₂ was significantly shifted to the visible light region. The photocurrent and photocatalytic activity of pure and doped TiO₂ were evaluated with the degradation of methyl orange (MO) and methylene blue (MB) solution under both UV and visible light illumination. The doped TiO₂ nanoparticles exhibit higher catalytic activity under each of visible light and UV irradiation in contrast to pure TiO₂. The photocatalytic activity and photocurrent ability of TiO₂ have been enhanced by doping of the titania in the following order: (Cu, N) - codoped TiO₂ > N-doped TiO₂ > Cu-doped TiO₂ > TiO₂. COD result for (Cu, N)-codoped TiO₂ reveals ∼92% mineralization of the MO dye on six h of visible light irradiation.     

Photocatalytic Activity of High Aspect Ratio TiO2 Nanorods

In this article, TiO₂ nanorods (aspect ratio >20) were prepared through a polyol process and doped with metal ions (Cu²⁺, Ni²⁺, Fe³⁺, and Cr³⁺). Compared with TiO₂ nanoparticles, the TiO₂ nanorods displayed relatively higher photocatalytic activity for the degradation of copper sulfophthalocyanine. Moreover, the photocatalytic activity was greatly enhanced when the metal ions were doped in the TiO₂ nanorods.     

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。     

Degradation of chemical warfare agents by nickel doped titanium dioxide powders: Enhanced surface activity

Here, Nickel doped anatase TiO₂ samples were prepared and characterized by X-ray diffraction, transmission electron microscope, X-ray photoelectron spectroscopy, specific surface area (BET), porosity determination (BJH) and CO₂-TPD experiments. DFT calculation was conducted to investigate the oxygen vacancy formation energies and hydroxyl groups activity. The as-prepared Ni²⁺ doped TiO₂ samples were used for heterogeneous degradation of chemical warfare agents (CWAs) and a high degradation rate, 92.2% and > 99.5% for sulfur mustard (HD) within 1 h and 12 h, > 99.5% for soman (GD) in less than 30 min, and > 99.5% for VX in less than 5 min was achieved, which were significantly enhanced compared with commercial P25 and anatase TiO₂ nanoparticles under identical conditions. The formation of non-toxic hydrolysis products confirmed the nucleophilic hydrolysis pathway via surface reaction. Integration of experimental and computational methods could well illustrate that surface structure changes of TiO₂ after Ni²⁺ doping was the main reason for the superior stoichiometric activity towards CWAs.     

Modification of nano-hybrid silicon acrylic resin with anticorrosion and hydrophobic properties

Silicone-acrylic resin (SAR) was prepared from acrylic monomers and silicone prepolymer by the free radical solution polymerization, and then mixed TiO₂ and SiO₂ nanoparticles modified by KH570 were added to prepare nanocomposite coating. Thermogravimetric analysis and contact angle measurements showed that the acrylic resin modified by silicone prepolymer exhibited an improved thermostability and a better hydrophobicity compared with the unmodified sample. The adding of nanoparticles further increased the hydrophobicity. The contact angle of modified silicone-acrylic resin with mixed TiO₂ and SiO₂ nanoparticles of 3 wt% is the highest, 108.4°. The UV resistance and weather resistance of the modified silicone-acrylic resin are significantly improved. It was also found through electrochemical impedance spectroscopy that the corrosion resistance was significantly improved by the addition of mixed TiO₂ and SiO₂ nanoparticles. Modified silicone-acrylic resin with mixed TiO₂ and SiO₂ nanoparticles of 3 wt% and 5 wt% coating system maintains an excellent anticorrosion performance (coating resistance R_c of more than 10⁹ Ω cm²) even at 3.5% NaCl electrolyte medium till to 1800 h.     

Effect of TiO<Subscript>2</Subscript> surface modification in Rhodamine B photodegradation

Commercial TiO₂ nanoparticles were superficially modified through polymeric resins obtained from polymerization of citrate complexes of Y³⁺ and Al³⁺ with ethylenglycol. The materials were treated at 450 °C for 4 h to obtain modified nanoparticles, which were characterized by HR-TEM, Zeta potential and surface area through N₂ fisisorption. Rhodamine B photodegradation by visible light irradiation and in presence of those modified nanoparticles was compared with the same process in presence of unmodified commercial TiO₂ nanoparticles. It was observed, by UV–visible spectroscopy, that the catalytic photoactivity in presence of modified nanoparticles was smaller than that observed with commercial TiO₂ nanoparticles. However, the surface modifier played an important role in the photodegradation kinetic process, showing a non-linear relation between modifier amount and photodegradation rate, presenting a maximum value at 0.8% (w/w).     

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。     

Solar active nano-TiO2 for mineralization of Reactive Red 120 and Trypan Blue: 1st Nano Update

Nano-TiO₂ was synthesized by sol–gel method. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) images, transmission electron microscope (TEM), BET surface area measurement and DRS analysis. The formation of anatase phase nano-TiO₂ was confirmed by XRD measurements and its crystalline size is found to be 15.2 nm. SEM images depict the crystalline nature of prepared TiO₂. The BET surface area of prepared TiO₂ is found to be 86.5 m² g^?1 which is higher than that of commercially available TiO₂–P25. The photocatalytic activity of prepared anatase phase TiO₂ has been tested for the degradation of two azo dyes: Reactive Red 120 (RR 120) and Trypan Blue (TB) using solar light. The photocatalytic activity of nano-TiO₂ is higher than TiO₂–P25 under solar light. The mineralization of dyes has been confirmed by chemical oxygen demand (COD) measurements.     

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.     

Modifications of pure and Ag doped TiO2 by pre-sulphated and calcination temperature treatments

Pre-sulphated pure and Ag doped TiO₂ photocatalysts were prepared by a modified low cost liquid impregnation method followed by acid (H₂SO₄) treatments. Surface and morphological characterizations of the prepared samples as well as their photocatalytic activity towards methyl orange (MO) were studied. The influence of sulphate pretreatment on the surface of pure TiO₂, the dispersion of deposit metals and the particle size were analyzed for the samples exposed to different calcination temperature (i.e. 500, 600 and 700 °C) treatments. The physical characterizations of the photocatalysts were investigated using diffused reflectance spectroscopy (UV–Vis DRS), XRD, BET, TEM, SEM and EDX analyses. The Kubelka–Munk function was used to determine the band gap energy for all prepared samples, whereby the band gap energy of pre-sulphated 1% Ag doped TiO₂ was found to be reduced to 2.95 eV. Photocatalytic activity towards the degradation of MO was found to be enhanced between 30 and 37% for the 1% Ag/TiO₂-S compared to the undoped TiO₂-S samples. The pre-sulphated sample of 1% Ag/TiO₂-S calcined at 700 °C showed up to 80% degradation of MO under normal compact fluorescent light.

     

Photoelectrocatalytic degradation of ethylene by a combination of TiO2 and activated carbon felts

Postharvest loss of quality is an important problem in the food and horticultural product industry. One of the major factors contributing to loss of quality is the uncontrolled exposure of the products to small amounts of ethylene gas during storage. In this study we investigated the photoelectrocatalytic (PEC) degradation of ethylene gas at a temperature of 3 ± 1 °C and relative humidity of 90 ± 3% on an activated carbon felts (ACF)-supported photocatalyst titanium dioxide photoelectrode [TiO₂/ACF] or on a photoelectrode which had been modified by coating the ACF support with platinum [TiO₂/ACF-Pt]. The apparent pseudo-first-order kinetic model was used to describe the PEC degradation of ethylene. The key designing parameters for a PEC reactor affecting the degradation efficiency in terms of the rate constant of this model were studied, including the bias voltage and the light intensity. Degradation of ethylene by applying a bias voltage to the [TiO₂/ACF] |Nafion|[TiO₂/ACF] electrode-membrane assembly or to the [TiO₂/ACF-Pt] |Nafion|[TiO₂/ACF-Pt] electrode-membrane assembly enhanced the efficiency of photocatalytic (PC) degradation. The combination of the ACF support modified with platinum and the applied bias voltage were found to have an additive enhancement effect on the rate constant compared to PEC degradation carried out using the unmodified ACF support. With respect to the [TiO₂/ACF-Pt] |Nafion|[TiO₂/ACF-Pt] electrode-membrane assembly, a kinetic model was established using response surface methodology to describe the relationship between the rate constant and the affecting parameters. Optimized parameters were found to be a light intensity of 3.1 mW cm⁻² with a bias voltage of 47.5 V.     

Catalytic Properties of TiO<Subscript>2</Subscript>/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles in Plasma Chemical Treatment

We proposed here a new process coupling dielectric barrier discharge (DBD) plasma with magnetic photocatalytic material nanoparticles for improving yield in DBD degradation of methyl orange (MO). TiO₂ doped Fe₃O₄ (TiO₂/Fe₃O₄) was prepared by the sol-gel method and used as a new type of magnetic photocatalyst in DBD system. It was found that the introduction of TiO₂/Fe₃O₄ in DBD system could effectively make use of the energy generated in DBD process and improve hydroxyl radical contributed by the main surface Fenton reaction, photocatalytic reaction and catalytic decomposition of dissolved ozone. Most part of MO (88%) was degraded during 30 min at peak voltage of 13 kV and TiO₂/Fe₃O₄ load of 100 mg/L, with a rate constant of 0.0731 min^?1 and a degradation yield of 7.23 g/(kW h). The coupled system showed higher degradation efficiency for MO removal.     

Synthesis of TiO<Subscript>2</Subscript> using different hydrolysis catalysts and doped with Zn for efficient degradation of aqueous phase pollutants under UV light

In this work, various TiO₂ and TiO₂ doped with 0.1, 1.0, and 5.0 mol% of Zn were prepared by the sol–gel method varying different hydrolysis catalysts (HNO₃, OHAc, H₃PO₄) in order to be used as photocatalysts for environmental applications. The X-ray diffraction results showed that the different TiO₂ samples have presented the anatase as main phase, However, the acid nature has played an important role in the superficial and optical properties. The N-physisortion analysis has revealed that the specific surface area of calcined TiO₂ samples prepared using H₃PO₄, HOAc, and HNO₃ was 245, 100, and 90 m² g⁻¹, respectively, while the spectroscopic UV analysis, the band gap energy has shifted by 3.3–3.0 eV. In order to improve the optical properties of TiO₂, the last preparation was doped with different zinc concentrations. The result showed that, as the Zn concentration increase by 0.1–5.0 mol%, the surface area increased from 90 to 120 m² g⁻¹. Nevertheless, the E _g returned from 3.0 to 3.32. The SEM analyses have not revealed important morphological changes between no doped and doped materials. The catalytic activity of the composite was studied on the photocatalytic degradation of 2,4-Dichlorophenoxyacetic acid (2,4-D) and the activity results showed that small Zn concentrations decrease the t _1/2 in 28 min.     

Solar light-induced photodegradation of chrysene in seawater in the presence of carbon-modified n-TiO2 nanoparticles

Photocatalytic degradation of chrysene in polluted seawater was successfully achieved under illumination of natural sunlight using carbon modified titanium oxide (C-TiO₂) nanoparticles. The morphological and structural characteristics of the as-synthesized nanoparticles were investigated by X-ray diffraction (XRD), UV–Vis spectra, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS). The characterization results confirmed the successful incorporation of carbon into C-TiO₂ nanoparticles. As a result of C-modification, a significant enhancement of the photocatalytic degradation efficiency was observed for C-TiO₂, compared with pure TiO₂. In order to optimize the operating parameters, the impacts of catalyst loading and pH on the photocatalytic degradation of chrysene were investigated. The best degradation rate was obtained at pH 3 and C-TiO₂ loading of 1.0 g L⁻¹. The photodegradation of chrysene in seawater by using C-TiO₂ was found to follow a pseudo first-order kinetics in terms of the Langmuir-Hinshelwood model.     

Photocatalytic degradation of methylene blue on Fe3+-doped TiO2 nanoparticles under visible light irradiation

Fe³⁺-doped TiO₂ composite nanoparticles with different doping amounts were successfully synthesized using sol-gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultravioletvisible spectroscopy (UV-Vis) diffuse reflectance spectra (DRS). The photocatalytic degradation of methylene blue was used as a model reaction to evaluate the photocatalytic activity of Fe³⁺/TiO₂ nanoparticles under visible light irradiation. The influence of doping amount of Fe³⁺ (ω: 0.00%–3.00%) on photocatalytic activities of TiO₂ was investigated. Results show that the size of Fe³⁺/TiO₂ particles decreases with the increase of the amount of Fe³⁺ and their absorption spectra are broaden and absorption intensities are also increased. Doping Fe³⁺ can control the conversion of TiO₂ from anatase to rutile. The doping amount of Fe³⁺ remarkably affects the activity of the catalyst, and the optimum efficiency occurs at about the doping amount of 0.3%. The appropriate doping of Fe³⁺ can markedly increase the catalytic activity of TiO₂ under visible light irradiation. __________ Translated from Journal of Northwest Normal University (Natural Science), 2006, 42(6): 55–56 [译自: 西北师范大学学报(自然科学版)]