Comparison of photocatalysis degradation of 4-nitrophenol using N,S co-doped TiO2 nanoparticles synthesized by two different routes

The photocatalytic degradation of 4-nitrophenol as pollutant in aqueous solutions was investigated under visible light irradiation over two different N?CS-codoped anatase TiO₂ catalysts prepared by sol?Cgel methods using titanium isopropoxide and titanium tetrachloride as two different precursors. The catalysts were characterized by XRD, SEM, DRS, EDAX and FT-IR. The effects of various operating parameters including the initial concentration of 4-nitrophenol (2?C14?ppm), solution pH (5?C8) and kinetic reactions were studied. The optimum solution pH was at around 6. For comparison purpose, the photodegradation activity of the commercial Degussa P-25 TiO₂ catalyst has also been studied. The results indicated that photocatalytic activity of N?CS-codoped TiO₂ with titanium isopropoxide as precursor was higher than N?CS-codoped TiO₂ with titanium tetrachloride as precursor and Degussa P-25.     

Vapor-thermal preparation of highly crystallized TiO2 powder and its photocatalytic activity

Nanocrystalline anatase TiO₂ powder photocatalysts were synthesized by a vapor-thermal method using tetrabutyl titanate as precursor at a temperature range from 120 to 200 °C. The as-synthesized products were characterized by X-ray diffraction, N₂ adsorption-desorption measurement, transmission electron microscopy, high resolution transmission electron microscopy, Fourier transform infrared spectra, Raman spectra, and their photocatalytic activity was evaluated by photocatalytic oxidation decomposition of acetone in air. The results showed that reaction temperature greatly affected the microstructures and photocatalytic activity of the samples. With increasing reaction temperature and time, the average crystalline size of TiO₂ particles increased and their crystallization enhanced, while the specific surface area of the products decreased. The TiO₂ powders obtained at a temperature range from 150 to 200 °C for 10 h showed good photocatalytic activity and were greatly higher than that of Degussa P-25.     

Synthesis and Comparative Study of Nano-TiO2 Over Degussa P-25 in Disinfection of Water

Nanostructured TiO₂ crystals were synthesized by gel to crystalline conversion. The crystals obtained were anatase form of titania averaging in 30 nm particles with an intrinsic band gap of 3.1 eV. The photocatalytic behavior was evaluated for the bactericidal effect in water, contaminated with the indicator organism Escherichia coli. The 100% photoinactivation of E. coli was achieved within 60 min with suspended nano-TiO₂. The catalytic activity of synthesized nanosample was observed to be 2.6 times more than that of commercial TiO₂ sample referred to as Degussa P-25. The photoinactivation of E. coli was tested with irradiation source of different wavelengths to substantiate the influence of particle size and nano crystallinity on electronic band structure. The photoactivity of nano titania enhanced to 1.625 times when the source of irradiation shifted from 360 to 400 nm while Degussa P-25 showed no change.     

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.     

Synergistic effect between TiO2 sol–gel and Degussa P25 in dye photodegradation

The TiO₂ powders were synthesized by versatile and low cost sol–gel process using HNO₃ and titanium tetra-isopropoxide (volumetric ratio of 4:1) following by the hydrolysis reaction. The powders show the two polymorphs of TiO₂: 96 % anatase and 4 % brookite, due to acidic condition (pH = 3). Thin films of titanium oxide were obtained by dip-coating, using the sol–gel of titanium oxide mixed with commercial Degussa P25 into a weight ratio 1:1 or 1:1.5, to enhance the synergistic effect of anatase/rutile ratio aiming at increasing the efficiency of the TiO₂ photocatalyst in dyes degradation. The thin film surface (charge and morphology) was controlled by polymer (poly-ethylene glycol) and surfactant (Sodium dodecyl sulphate, Triton X100) addition. The titanium oxide was characterized by particle size analyzer, contact angle measurements, X-ray diffraction, scanning electron microscopy, and atomic force microscopy. The photocatalytic properties of powders and coatings were evaluated based on the degradation efficiency of two reference dyes (methyl orange and methylene blue). The results outline that poly(ethylene glycol) and films morphologies are the most influential factors that affecting the photocatalytic activity.     

Samarium-doped mesoporous TiO2 nanoparticles with improved photocatalytic performance for elimination of gaseous organic pollutants

Mesoporous TiO₂ doped with different amounts of Sm were prepared via a sol-gel route with Pluronic P123 as template. The materials were characterized by X-ray diffraction, transmission electron microscopy, and N₂ sorption experiments, etc. The photocatalytic activity of the mesoporous TiO₂ was tested in elimination of gaseous methanol and acetone. The Sm doped mesoporous TiO₂ have higher activity than those of the commercial photocatalyst (Degussa, P25) and Sm doped TiO₂ counterparts without mesopore structure under ultraviolet light irradiation. A possible mechanism was proposed to account for the high photocatalytic activity of the Sm doped mesoporous TiO₂. The superior activity of the Sm doped mesoporous TiO₂ may be attributed to the synergic effect of the high surface area, mesopore structure and doped Sm species.     

Flame synthesis of TiO2 nanoparticles with high photocatalytic activity

Growth behaviour of TiO₂ particles, which has significant influence on their crystallinity and surface area, has been controlled by varying the process parameters of the flame aerosol synthesis. An existing method to determine the crystallinity of the powder has been modified which facilitates comparison of the degree of crystallinity of the nanoparticles synthesized by various methods. Resultant TiO₂ nanoparticles were characterized by XRD and nitrogen physisorption to determine the degree of crystallinity quantitatively and surface area, respectively, and the decomposition rate of an industrial dye, methylene blue, has been taken as the measure of the photocatalytic activity (PCA). TiO₂ nanoparticles showed improved photocatalytic activity compared to the commercial photocatalyst, Degussa P25. This is attributed to the increased degree of crystallinity and surface area of the TiO₂ nanoparticles compared to Degussa P25. The results of this study elucidate the importance of the gas-phase processes and strategy to synthesize highly active TiO₂ photocatalysts in a single step. Moreover, difference in the PCA of the nanoparticles synthesized by the similar gas-phase routes has been shown and the particles are tailor-made for improved PCA in the present study.     

Nanodisperse photocatalysts based on titanium dioxide

A new method for synthesizing amorphous ultradisperse titanium oxide particles immobilized on the surface of SiO₂ aerogel was suggested. TiO₂/SiO₂ systems containing 3–15 wt % TiO₂ were prepared. The chemical composition, structure, and morphology of the surface of the synthesized catalysts were studied by transmission electron microscopy, X-ray diffraction, and IR spectroscopy. The Brunauer-Emmett-Teller method was used to estimate the specific surface area of the samples. The photocatalytic activity of the systems was studied in the model reaction of the decomposition of methylene blue dye. The systems synthesized were found to be more active than TiO₂ Degussa P25.     

Synthesis of bimodal porous structured TiO2 microsphere with high photocatalytic activity for water treatment

In this work bimodal structured titanium dioxide (TiO₂) microsphere has been prepared from commercial TiO₂ powder and nano-sized titania gel via sol–gel spray-coating technique. Crystallization and transformation behavior of titania gel were investigated. The results revealed that the crystallization and transformation of anatase particles were substantially affected by the concentration of solvent and calcination temperature. Anatase crystallite size of 10 nm was obtained at mole ratio of solvent/precursor 50/1 and calcination temperature of 450 °C. The prepared nano-sized titania gel was embedded within the core (commercial TiO₂, P25) during the spraying process. The prepared TiO₂ microsphere was characterized using X-ray diffractometer (XRD), scanning electron microscope (SEM), field emission electron microscope (FESEM) and micropore analysis. The photocatalytic activity was monitored by following the degradation of phenol with activity benchmarked against commercial P25 (Degussa). The increase of photocatalytic activity of TiO₂ microsphere was attributed to the nano-sized anatase crystallite which has been incorporated into the TiO₂ microsphere.     

Microwave‐Hydrothermal Preparation and Visible‐Light Photoactivity of Plasmonic Photocatalyst Ag‐TiO2 Nanocomposite Hollow Spheres

Visible‐light‐driven plasmonic photocatalyst Ag‐TiO₂ nanocomposite hollow spheres are prepared by a template‐free chemically‐induced self‐transformation strategy under microwave‐hydrothermal conditions, followed by a photochemical reduction process under xenon lamp irradiation. The prepared samples are characterized by using scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, N₂ adsorption‐desorption isotherms, X‐ray photoelectron spectroscopy, UV/Vis and Raman spectroscopy. Production of ?OH radicals on the surface of visible‐light illuminated TiO₂ was detected by using a photoluminescence method with terephthalic acid as the probe molecule. The photocatalytic activity of as‐prepared samples was evaluated by photocatalytic decolorization of Rhodamine B (RhB) aqueous solution at ambient temperature under visible‐light irradiation. The results show that the surface plasmon absorption band of the silver nanoparticles supported on the TiO₂ hollow spheres was red shifted, and a strong surface enhanced Raman scattering effect for the Ag‐TiO₂ nanocomposite sample was observed. The prepared nanocomposite hollow spheres exhibits a highly visible‐light photocatalytic activity for photocatalytic degradation of RhB in water, and their photocatalytic activity is higher than that of pure TiO₂ and commercial Degussa P25 (P25) powders. Especially, the as‐prepared Ag‐TiO₂ nanocomposite hollow spheres at the nominal atomic ratio of silver to titanium ( R ) of 2 showed the highest photocatalytic activity, which exceeds that of P25 by a factor of more than 2.     

Photodegradation of Direct Blue-199 in carpet industry wastewater using iron-doped TiO2 nanoparticles and regenerated photocatalyst

Fe-doped TiO_2, Ti_1–xFe_xO₂ (x = 0.00, 0.02, 0.04, 0.06, 0.08, and 0.10), photocatalysts have been successfully synthesized via citric acid–assisted autocombustion method. The synthesized photocatalysts were characterized using different characterization techniques, such as X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDX), and x-ray photoelectron spectroscopy (XPS). The XRD diffraction patterns revealed that synthesized photocatalysts have the anatase phase of TiO₂. The DRS analysis indicates a slight increment in absorbance in the visible light region by the Fe doping in TiO₂. The FT-IR spectra reveal the various stretching and bending vibrational bands of the Ti–O lattice. The XPS spectra confirm the presence of elements titanium, oxygen, and iron in the synthesized samples and determine binding energy of elements. TEM analysis shows the shape of the synthesized photocatalyst, and it was used to calculate the average particle sizes of undoped and Fe-doped TiO₂ (Ti_0.96Fe_0.04O₂) photocatalysts using a histogram. The photocatalytic activities of synthesized photocatalysts were determined by photodegradation of dye (Direct Blue 199), contaminating carpet industry wastewater in the photochemical reactor and open pan reactor. The maximum photodegradation activity was shown by the Ti_0.96Fe_0.04O₂ photocatalyst among all the synthesized undoped and Fe-doped photocatalysts. The synthesized photocatalyst (Ti_0.96Fe_0.04O₂) had better photocatalytic activity when compared to both, undoped TiO₂ and Aeroxide (Degussa) P-25. The used Fe-doped TiO₂ photocatalyst (Ti_0.96Fe_0.04O₂) was regenerated five times and investigated for its photocatalytic activity.     

Low Temperature Solvent Evaporation-induced Crystallization Synthesis of Nanocrystalline TiO2 Photocatalyst

A novel and efficient methodology for obtaining highly active photocatalyst of bi-phase TiO2 with small particle size and high specific surface area was developed by solvent evaporation-in-duced crystallization (SEIC) method at low temperature. The prepared TiO2 powder was characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET surface areas. The photocatalyfic activity was evaluated by the photocatalyflc oxidation of acetone in air. The results showed that the photocatalytic activity of the TiO2 powder preDared by this method approached that of Degnssa P25. This may be atotributed to the fact that the predated TiO2 powder had larzer specific surface areas (265 m2. g- 1 ) and smaller crystallite size (about 5 nm), but relatively low crystallinity, as compared with Degussa P25.     

Photocatalytic applications of Au-deposited on TiO2 nanocomposite catalyst in dye degradation via photoreduction

The photocatalytic activity of gold deposited on Degussa P25 titanium dioxide (Au-DP25) in the photodegradation of methyl orange (MO) was investigated. The as-prepared materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (DRS) techniques. The obtained results show that the gold (Au⁰) deposited TiO₂ exhibited visible light plasmon absorption band. The degradation experiment j reveals that the catalytic activity of Au-DP25 in the degradation of MO is higher than that of commercially available Degussa P25 TiO₂ (DP25) samples. In addition, the photocatalytic ability of composite Au-DP25 was hardly decreased after a five-cycle for MO degradation. The kinetics of the MO degradation fitted well the Langmuir-Hinshelwood model.     

Development of TiO2 pastes modified with Pechini sol–gel method for high efficiency dye-sensitized solar cell

A titanium oxide layer used for a dye-sensitized solar cell (DSSC) has to meet two opponent properties to assure a high efficiency DSSC: good connection between TiO₂ grains and a large inner surface area. Three different paste formulations based on commercial nanocrystalline TiO₂ powder (Degussa P25) are studied. Results confirm that modification of the TiO₂ paste with the Pechini sol–gel method increases the surface area of the TiO₂ layer while maintaining good connections between the nanocrystalline grains, consequently the efficiency of the DSSC increases from 1.8% to 5.3%. The structure and morphology of the TiO₂ layers are described by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD).     

Surface properties and photocatalytic activity of nanocrystalline titania films

In this work the efficiency and physicochemical details of a thin film produced by help of a microwave assisted sol gel technique is compared to different commercial powders (Degussa P25 and Hombikat UV100) deposited on glass substrates. Furthermore, a supercritical produced TiO₂ powder (SC 134) was included in the comparison.The prepared TiO₂ films were characterized using XRD, XPS, AFM, DSC and DLS. The photocatalytic activity was determined using stearic acid as a model compound. Investigation of the prepared films showed that the Degussa P25 film and the sol–gel film were the most photocatalytic active films. The activity of the films was found to be related to the crystallinity of the TiO₂ film and the amount of surface area and surface hydroxyl groups. Based on the XPS investigation of the films before and after UV irradiation it was suggested that the photocatalytic destruction of organic matter on TiO₂ films proceeds partly through formation of hydroxyl radicals which are formed from surface hydroxyl groups created by interactions between adsorbed water and vacancies on the TiO₂ surface. Furthermore a correlation between the amount of OH groups on the surface of the different TiO₂ films and the photocatalytic activity was found.     

A credible role of copper oxide on structure of nanocrystalline mesoporous titanium dioxide

Copper oxide-titania catalysts with nanocrystalline mesoporous structure were prepared by sol-gel technique using tetra isopropyl ortho titanate (TiPT) as the inorganic precursor and amino-2 ethanol as the swelling agent. Characterization was performed using X-ray diffraction (XRD), fourier transformed infrared spectra (FTIR), scanning electron microscopy (SEM), diffuse reflectance UV-Vis spectroscopy (DRS), and N₂ adsorption-desorption measurements. It was found that CuO (0.025–0.1 mol ratio) has some effect on the particle size, surface area, pore-volume, pore-diameter, crystallinity of the particles, and crystalline phase of TiO₂ nanocrystalline. The results indicated that 0.1 CuO-TiO₂ had higher surface area and total pore volume among all CuO-TiO₂ samples. The SBET value of 0.1 mol ratio CuO-load TiO₂ sample is approximately similar to that of Degussa P25 while its pore volume (0.1198 cm³ g^?1) is larger than Degussa P25 due to production of large number of pores. Therefore, the physical property of 0.1 CuO-TiO₂ catalyst is comparable with Degussa P25.At 823K, the 0.1 mol ratio CuO-load TiO2 sample shows the phase transformation from anatase to rutile in the ratio of 1:1.1. The synthesized CuO-TiO₂ nanocrystalline will be able to show photocatalytic reaction under visible light.     

Visible light photodegradation of dyes over mesoporous titania prepared by using chrome azurol S as template

Mesoporous TiO₂ with anatase crystalline structure (MTiO₂/CAS) has been synthesized by using chrome azurol S (CAS, 2″,6″-dichloro-3,3′-dimethyl-4′-hydroxy-3″-sulfofuchson-5,5′-dicarboxylic acid) as template. It was characterized by X-ray diffraction, nitrogen adsorption/desorption, diffuse reflectance UV–visible and FT-IR spectrometry, and transmission electron microscopy. It was found that MTiO₂/CAS had substantial photocatalytic activity in the degradation of methylthionine chloride, rhodamine B, gentian violet, safranin T, methyl violet, and fuchsine basic whereas Degussa P25 (P25) had negligible photodegradation yield (<6%) under visible light irradiation.     

Photocatalytic degradation of methyl methacrylate copolymers

The photolytic and photocatalytic degradation of the copolymers poly(methyl methacrylate-co-butyl methacrylate) (MMA-BMA), poly(methyl methacrylate-co-ethyl acrylate) (MMA-EA) and poly(methyl methacrylate-co-methacrylic acid) (MMA-MAA) have been carried out in solution in the presence of solution combustion synthesized TiO₂ (CS TiO₂) and commercial Degussa P-25 TiO₂ (DP 25). The degradation rates of the copolymers were compared with the respective homopolymers. The copolymers and the homopolymers degraded randomly along the chain. The degradation rate was determined using continuous distribution kinetics. For all the polymers, CS TiO₂ exhibited superior photo-activity compared to the uncatalysed and DP 25 systems, owing to its high surface hydroxyl content and high specific surface area. The time evolution of the hydroxyl and hydroperoxide stretching vibration in the Fourier transform-infrared (FT-IR) spectra of the copolymers indicated that the degradation rate follows the order MMA-MAA > MMA-EA > MMA-BMA. The same order is observed for the rate coefficients of photocatalytic degradation. The photodegradation rate coefficients were compared with the activation energy of pyrolytic degradation. In degradation by pyrolysis, it was observed that MMA-BMA was the least stable followed by MMA-EA and MMA-MAA. The observed contrast in the order of thermal stability compared to the photo-stability of these copolymers was attributed to the two different mechanisms governing the scission of the polymer and the evolution of the products.     

Hierarchical chlorine-doped rutile TiO2 spherical clusters of nanorods: Large-scale synthesis and high photocatalytic activity

In this study, we report the synthesis of hierarchical chlorine-doped rutile TiO₂ spherical clusters of nanorods photocatalyst on a large scale via a soft interface approach. This catalyst showed much higher photocatalytic activity than the famous commercial titania (Degussa P25) under visible light (λ>420 nm). The resulting sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), nitrogen adsorption, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy, ¹H solid magic-angle spinning nuclear magnetic resonance (MAS-NMR) and photoluminescence spectroscopy. On the basis of characterization results, we found that the doping of chlorine resulted in red shift of absorption and higher surface acidity as well as crystal defects in the photocatalyst, which were the reasons for high photocatalytic activity of chlorine-doped TiO₂ under visible light (λ>420 nm). These hierarchical chlorine-doped rutile TiO₂ spherical clusters of nanorods are very attractive in the fields of environmental pollutants removal and solar cell because of their easy separation and high activity.     

不同氮源溶剂热合成N-TiO2纳米颗粒及其光催化降解气相苯（英文）

采用三种不同的氮源溶剂热合成了锐钛矿-板钛矿混晶的N-TiO2催化剂.采用X射线衍射、N2吸附-脱附、X射线光电子能谱和透射电子显微镜等手段对催化剂进行了表征.重点研究了不同氮源对催化剂的相组成、晶粒尺寸、微观结构以及比表面积的影响.采用紫外光降解气相苯测试了合成材料的催化活性.结果表明,以水合肼为氮源合成的N-TiO2表现出最优的光催化活性,其活性明显高于P25,且能够循环使用15次以上.采用气相色谱-质谱技术分析了光降解过程的中间产物,基于此提出了相应的降解机理.