Degradation of nitrobenzene using titania photocatalyst co-doped with nitrogen and cerium under visible light illumination

A type of nitrogen and cerium co-doped titania photocatalyst, which could degrade nitrobenzene under visible light irradiation, was prepared by the sol-gel route. Titanium isopropoxide, ammonium nitrate, and cerium nitrate were used as the sources of titanium, nitrogen, and cerium, respectively. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffusive reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and N(2) adsorption-desorption isotherm were employed to characterize the as-prepared photocatalyst. The degradation of nitrobenzene under visible light illumination was taken as probe reaction to evaluate the photoactivity of the co-doped photocatalyst. The commercial TiO(2) photocatalyst (Degussa P25), which was thought as a high active photocatalyst, was chosen as standard photocatalyst to contrast the photoactivity of the nitrogen and cerium co-doped titania photocatalyst. The results showed that the photocatalytic performance of the nitrogen and cerium co-doped titania was related with the calcination temperature and the component. The nitrogen atoms were incorporated into the crystal of titania and could narrow the band gap energy. The doping cerium atoms existed in the forms of Ce(2)O(3) and dispersed on the surface of TiO(2). The improvement of the photocatalytic activity was ascribed to the synergistic effects of the nitrogen and cerium co-doping.     

S、RE共掺杂TiO2的制备及其可见光分解水制氢性能

采用溶胶-凝胶法制备了系列稀土(La、Eu、Nd、Tb、Er)和硫共掺杂TiO2光催化剂RE/S/TiO2。通过紫外-可见(UV-Vis)漫反射、X射线衍射(XRD)对催化剂进行了表征。以EDTA为电子给体,考察了光催化剂在可见光照射下的制氢活性。研究结果表明,S/TiO2具有可见光活性,稀土掺杂进一步提高了S/TiO2可见光活性,其活性顺序依次为Eu/S/TiO2>La/S/TiO2>Nd/S/TiO2>Tb/S/TiO2>Er/S/TiO2。与纯TiO2和S/TiO2光催化剂相比,稀土掺杂使催化剂的粒径减小,晶格畸变应力增大,从而提高了催化剂可见光制氢活性。     

The effect of erbium on the adsorption and photodegradation of orange I in aqueous Er3+-TiO2 suspension

Pure TiO(2) and erbium ion-doped TiO(2) (Er(3+)-TiO(2)) catalysts prepared by the sol-gel method were characterized by means of XRD and diffusive reflectance spectra (DRS). The XRD results showed that erbium ion doping could enhance the thermal stability of TiO(2) and inhibit the increase of the crystallite size, and the DRS results showed that the optical absorption edge slightly shifted to red direction owing to erbium ion doping and the Er(3+)-TiO(2) catalysts had three typical absorption peaks located at 490, 523 and 654 nm owing to the transition of 4f electron from (4)I(15/2) to (4)F(7/2), (2)H(11/2) and (4)F(9/2). With a purpose of azo dyes degradation, orange I was used as a model chemical. And the adsorption isotherm, degradation and mineralization of orange I were investigated in aqueous suspension of pure TiO(2) or Er(3+)-TiO(2) catalysts. The results showed that Er(3+)-TiO(2) catalysts had higher adsorption equilibrium constants and better adsorption capacity than pure TiO(2). The adsorption equilibrium constants (K(a)) of Er(3+)-TiO(2) catalysts were about twice of that of pure TiO(2). The maximum adsorption capacity (Q(max)) of 2.0% Er(3+)-TiO(2) catalyst was 13.08x10(-5)mol/g, which was much higher than that of pure TiO(2) with 9.03x10(-5)mol/g. Among Er(3+)-TiO(2) catalysts, 2.0% Er(3+)-TiO(2) catalyst achieved the highest Q(max) and K(a) values. The kinetics of the orange I degradation using different Er(3+)-TiO(2) catalysts were also studied. The results demonstrated that the degradation and mineralization of orange I under both UV radiation and visible light were more efficient with Er(3+)-TiO(2) catalyst than with pure TiO(2), and an optimal dosage of erbium ion at 1.5% achieved the highest degradation rate. The higher photoactivity under visible light might be attributable to the transitions of 4f electrons of Er(3+) and red shifts of the optical absorption edge of TiO(2) by erbium ion doping.     

Photodegradation of methyl orange by photocatalyst of CNTs/P-TiO(2) under UV and visible-light irradiation

A novel nanoscale photocatalyst CNTs/P-TiO(2) was successfully prepared by hydrothermal method. The morphology and the physicochemical properties of the prepared samples were investigated using TEM, XPS, XRD, BET, FTIR, TG-DSC and UV-vis DRS spectroscopy. The photocatalytic activity was evaluated by degradation of methyl orange (MO) dye. The results demonstrated that CNTs/P-TiO(2) nanoparticles could effectively photodegrade MO not only under UV irradiation but also under visible-light (VL) irradiation. The MO degradation performance on CNTs/P-TiO(2) was superior to that of the commercial P25. The optimal mass ratio of CNTs to P-TiO(2) in the nanocomposite catalyst was 5:100. The synergetic effect was discussed in terms of different roles played by phosphorus doping and introducing CNTs into the composite catalysts.     

Photocatalytic activity of La, Y Co-doped TiO2 nanoparticles synthesized by ultrasonic assisted sol-gel method

Bare TiO2 (T), La-doped TiO2 (LT), Y-doped TiO2 (YT), La, Y co-doped TiO2 (LYT) were successfully prepared by facile ultrasonic assisted sol-gel synthesis using Ti(OC4H9)4 as the precursor. The products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), UV-visible diffuse reflectance spectra (DRS), and X-ray photoelectron spectroscopy (XPS), respectively. The photocatalytic activities of anatase samples, with the average particle diameters ranging from 14 nm to 21 nm, were evaluated for photodegradation of methyl orange (MO). The XPS results indicated that Y atoms were incorporated into titania lattice, while La atoms existed on the crystal surface. Due to doping, the optical absorption edges of LT, YT, and LYT shifted to the visible light region by 21 nm, 29 nm and 35 nm, respectively. The photocatalytic performances of the doped samples, such as LT, YT and LYT, were much higher than that of bare TiO2 under UV-visible light irradiation. And the photoreactivity efficiency of the LYT was the highest. It indicated that a strong La-Y synergistic interaction appeared to play a decisive role in driving the excellent photocatalytic performance of titania.     

Preparation and photocatalytic activity of nanoglued Sn-doped TiO2

In this paper, Sn-doped TiO(2) photocatalyst was prepared and immobilized on a glass substrate using an about-to-gel SiO(2) sol as a nanoglue. The characterization of the Sn-doped TiO(2) by XRD showed that 5% Sn content is formed by anatase and rutile crystallites. Characterization of the nanoglued photocatalyst by the BET measurement, TEM, and SEM showed that the photocatalyst was a nanoporous material with a high-surface area. The Sn-doped TiO(2) was uniformly dispersed within the three-dimensional network of the silica in the form of nanoparticles. The nanoglued photocatalyst showed high photocatalytic activity during the degradation of penicillin under UV light. The effect of different Sn content on the amount of hydroxyl radical was discussed by using salicylic acid as probe molecules. The results show that an appropriate amount of Sn dopant can greatly increase the amount of hydroxyl radicals generated by TiO(2) nanoparticles, which are responsible for the obvious increase of photocatalytic activity.     

新型异质结LaCO3OH/In(OH)3/In2S3的制备及其可见光下催化降解罗丹明B的性能

采用原位湿化学方法合成了LaCO3OH/In(OH)3/In2S3异质结光催化剂。采用XRD、 SEM、 XPS、 BET、 TG等表征技术对所制备LaCO3OH/In(OH)3/In2S3异质结光催化剂的组成、结构和形貌等进行分析。以可见光下(λ≥420 nm)降解罗丹明B(RhB)为探针反应,研究了LaCO3OH含量不同时LaCO3OH/In(OH)3/In2S3异质结光催化剂的光催化活性。结果表明,当La/In的摩尔比为15mol%时, LaCO3OH/In(OH)3/In2S3异质结光催化剂具有最高的降解活性,与In(OH)3/In2S3相比,活性提高约一倍。这可能是由于LaCO3OH/In(OH)3/In2S3异质结光催化剂具有较高的比表面积、合适的能带结构和较好的吸附性能。以对苯二甲酸为探针分子,光催化实验证明羟基自由基(·OH)是重要的活性物种。并提出了可能的降解机制。     

Preparation and characterization of titania photocatalyst co-doped with boron, nickel, and cerium

A type of visible-light-induced titania photocatalyst co-doped with boron, nickel, and cerium was prepared by the sol–gel route. The microstructure and optical property of the ternary co-doped photocatalyst were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and UV–Vis diffusive reflectance spectroscopy (DRS). Its photoactivity was evaluated by the degradation of phenol under visible light illumination. It was testified that boron doping led to the response to visible light and that nickel and cerium doping prohibited the recombination of the photo-generated electron-hole pairs, improving the photocatalytic performance. The results showed that the synergistic effects of boron, nickel and cerium co-doping played an important role in raising photoactivity.     

TiO2纳米颗粒的制备、光催化性能及羟基自由基研究

采用聚丙烯酰胺凝胶法制备了TiO2纳米颗粒,利用X射线衍射、扫描电子显微镜和紫外．可见光漫反射光谱分别研究了不同煅烧温度对样品晶相、颗粒形貌和带隙的影响．以甲基橙（M0）为目标降解物,在紫外光照射下考察了制得的TiO2样品的光催化性能．研究结果表明,500℃煅烧制备的样品光催化性能最好;随着催化剂用量的增加,MO降解率呈现先增大后减小的趋势,最佳催化剂用量为4．0g／L;在pH值不太高时（≤7．2）,M0降解率随pH值的升高呈下降趋势．以香豆素为探测剂．采用荧光光谱检测催化剂在紫外光照射下产生羟基自由基（·OH）的情况,研究了煅烧温度、催化剂用量和溶液pH值对·0H产率的影响．研究结果还表明,·OH产率与MO降解率的变化规律基本一致,表明·0H可能是TiO2光催化降解有机染料的主要活性物种．     

溶胶-凝胶法制备TiO_2-Al_2O_3复合光催化剂及其表征

以钛酸四正丁酯为钛源,异丙醇铝为铝源,采用溶胶-凝胶法制备了TiO2-Al2O3复合光催化剂,考察其对甲基橙的吸附性能和在紫外光照射下的光催化活性。采用X射线衍射(XRD)、X射线光电子能谱(XPS)、傅里叶变换红外光谱(FT-IR)、N2吸附-脱附等对催化剂的晶相结构、化学组成及BET比表面积和孔径分布等进行了表征。结果表明TiO2-Al2O3复合光催化剂由TiO2和Al2O3组成,其中TiO2为单一的锐钛矿晶相,Al2O3为非晶态,Al2O3的存在可抑制TiO2晶粒的生长。在n(Ti)/n(Al)=12,500℃煅烧3h制得的TiO2-Al2O3复合光催化剂比表面积达99.21m2/g,平均孔径为22.39nm,累计孔容积为0.4493cm3/g。在500℃煅烧制得的复合光催化剂具有最佳的光催化活性和吸附性能。与纯TiO2相比,相同条件下TiO2-Al2O3复合光催化剂的光催化活性和吸附性能都有较大提高。     

Photoinduced hydroxyl radical and photocatalytic activity of samarium-doped TiO(2) nanocrystalline

Sm(3+)-doped TiO(2) nanocrystalline has been prepared by sol-gel auto-combustion technique and characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) method, and also UV-vis diffuse reflectance spectroscopy (DRS). These Sm(3+)-doped TiO(2) samples were tested for methylene blue (MB) decomposition and *OH radical formation. The analysis of *OH radical formation on the sample surface under UV irradiation was performed by fluorescence technique with using terephthalic acid, which readily reacted with *OH radical to produce highly fluorescent product, 2-hydroxyterephthalic acid. It was observed that the presence of Sm(3+) ion as a dopant significantly enhanced the photocatalytic activity for MB degradation under UV light irradiation because both the larger specific surface area and the greater the formation rate of *OH radical were simultaneously obtained for Sm(3+)-doped TiO(2) nanocrystalline. The adsorption experimental demonstrated that Sm(3+)-TiO(2) had a higher MB adsorption capacity than undoped TiO(2) and the adsorption capacity of MB increased with the increase of samarium ion content. The results also indicated that the greater the formation rate of *OH radical was, the higher photocatalytic activity was achieved. In this study, the optimum amount of Sm(3+) doping was 0.5 mol%, at which the recombination of photo-induced electrons and holes could be effectively inhibited, the highest formation rate of *OH radicals was, and thereby the highest photocatalytic activity was achieved.     

Characterization and activity of Pd-modified TiO2 catalysts for photocatalytic oxidation of NO in gas phase

Pd-modified TiO(2) prepared by thermal impregnation method was used in this study for photocatalytic oxidation of NO in gas phase. The physico-chemical properties of Pd/TiO(2) catalysts were characterized by X-ray diffraction analysis (XRD), Brunauer-Emmett-Teller measurements (BET), X-ray photoelectron spectrum analysis (XPS), transmission electron microscopy (TEM), high resolution-transmission electron microscopy (HR-TEM), UV-vis diffuse reflectance spectra (UV-vis DRS) and photoluminescence spectra (PL). It was found that Pd dopant existed as PdO particles in as-prepared photocatalysts. The results of PL spectra indicated that the photogenerated electrons and holes were efficiently separated after Pd doping. During in situ XPS study, it was found that the content of hydroxyl groups on the surface of Pd/TiO(2) increased when the catalyst was irradiated by UV light, which could result in the improvement of photocatalytic activity. The activity test showed that the optimum Pd dopant content was 0.05 wt.%. And the maximum conversion of NO was about 72% higher than that of P25 when the initial concentration of NO was 200 ppm, which showed that Pd/TiO(2) photocatalysts could be potentially applied to oxidize higher concentration of NO.     

Preparation and application of nanoglued binary titania-silica aerogel

Nanoglued binary titania (TiO2)-silica (SiO2) aerogel, as a novel type of photocatalyst, has been synthesized on glass substrates. Using an about-to-gel SiO2 sol as nanoglue, anatase TiO2 aerogel was immobilized into a three-dimensional mesoporous network of the SiO2. Factorial designs were employed to optimize both TiO2 aerogel and binary TiO2-SiO2 aerogel synthesis. Characterization of the as-prepared TiO2 and binary samples by surface area, porosity, and surface chemical composition showed that the photocatalysts were high-surface-area nanoporous materials, with a Ti4+ valency. The binary aerogel exhibited high photocatalytic activity for the degradation of methylene blue (MB) under simulated solar light; the reaction followed the pseudo first-order Langmuir-Hinshelwood (L-H) kinetic model. Fluorescence spectroscopy revealed that the hydroxyl (*OH) radical was formed during the illumination of the binary TiO2-SiO2 aerogel in a solution of probe molecules, which corroborates the probable mechanism of hydroxyl radical oxidation of contaminants in photocatalytic reactions.     

Oxygen-rich TiO2 decorated with C-Dots: Highly efficient visible-light-responsive photocatalysts in degradations of different contaminants

Providing novel photocatalysts with high photocatalytic efficiency is of great significance. In the present work, hydrogen peroxide and carbon dots (C-Dots) were utilized to enhance the photocatalytic performance of TiO₂ under visible light. The fabricated TiO₂-peroxo/C-Dots photocatalysts were analyzed by XRD, HRTEM, SEM, EDX, BET, FT-IR, XPS, PL, UV–Vis DRS, EIS, and photocurrent density. Photocatalytic abilities of the nanocomposites were evaluated by photocatalytic removal of RhB, MO, MB, fuchsine, and Cr (VI) upon visible-light illumination. The results demonstrated that the binary nanocomposites exhibited remarkably enhanced photocatalytic activity compared with the TiO₂ and TiO₂-peroxo photocatalysts. The best photocatalytic performance was obtained using 0.75?mL of C-Dots, which was approximately 79.2, 17.1, 71.4, and 40.5 times higher than the pure TiO₂ for degradations of RhB, MO, MB, and fuchsine, respectively. Furthermore, the TiO₂-peroxo/C-Dots nanocomposites exhibited high stability in consecutive photocatalytic processes. Based on the results, the TiO₂-peroxo/C-Dots photocatalyst is expected to become a promising photocatalyst for practical applications in water purification.     

多壁碳纳米管改性InVO4光催化剂的制备及性能

以酸处理的多壁碳纳米管(MWCNTs)为载体,采用水热合成法制备了InVO4/MWCNTs光催化剂.利用场发射扫描电镜、X射线粉末衍射、BET-N2吸附、傅里叶红外光谱和紫外-可见漫反射吸收光谱等技术对样品的形貌、晶相组成、比表面积和吸光性能等物理性质进行了表征,并以气相的苯作为模型污染物,研究催化剂样品在可见光(λ>420 nm)照射下的光催化氧化能力.结果表明,InVO4颗粒均匀附着于MWCNTs,表面粒径约100 nm.与纯InVO4相比,InVO4/MWCNTs的比表面积和可见光吸收性能显著提高.在可见光照射下,InVO4/MWCNTs具有良好的光催化活性,反应4 h光催化降解苯的转化率和矿化率分别为41.0%和43.4%,其转化率分别是InVO4的1.5倍和掺氮TiO2的3倍,InVO4/MWCNTs光催化活性的提高与载体MWCNTs良好的电子传输特性有关.     

Characterization of TiO(2)-chitosan/glass photocatalyst for the removal of a monoazo dye via photodegradation-adsorption process

In this paper, the newly explored TiO(2)-Chitosan/Glass was suggested as a promising alternative material to conventional means of wastewater treatment. Characterization of TiO(2)-Chitosan/Glass photocatalyst was studied with SEM-EDX, XRD, and Fourier transform infrared spectroscopy (FTIR) analysis. The combination effect of photodegradation-adsorption process for the removal of methyl orange (MO), an acid dye of the monoazo series occur promisingly when four layers of TiO(2)-Chitosan/Glass photocatalyst was used for MO removal. Approximately, 87.0% of total MO removal was achieved. The reactive -NH(2), -OH, and metal oxide contents in the prepared photocatalyst responsible for the photodegradation-adsorption effect were confirmed by FTIR study. Similarly, MO removal behavior was well supported by SEM-EDX and XRD analysis. Significant dependence of MO removal on the TiO(2)-Chitosan loading can be explained in terms of relationship between quantum yield of photocatalytic reactions and photocatalyst structure/activity. Hence, the research work done thus far suggests a new method, having both the advantages of photodegradation-adsorption process in the abatement of various wastewater pollutants.     

Mn、N共掺杂TiO_2负载竹质活性炭纤维的制备及可见光光催化性能

为研究Mn、N共掺杂TiO_2负载竹质活性炭纤维(Mn-N/TiO_2-BACF)的可见光光催化性能,首先,以MnSO_4·H_2O为锰源,尿素为氮源,采用溶胶-凝胶法制备了光催化复合材料Mn-N/TiO_2-BACF;然后,利用SEM、XRD及XPS等考察了煅烧温度对Mn-N/TiO_2-BACF结构和可见光光催化性能的影响。结果表明:Mn、N共掺杂使光催化复合材料的光响应范围由紫外光区域拓宽至可见光区域;随煅烧温度的提高,光催化复合材料表面的晶格氧含量逐渐降低,吸附氧含量先降低后增加,而羟基氧含量有所增加;光照400min后,350℃锻烧制备的Mn-N/TiO_2-BACF在可见光下对亚甲基蓝的光降解率达99.7%。同时,还发现Mn-N/TiO_2-BACF在可见光下的光降解率与煅烧温度没有相关性。     

ZnGaNO solid solution–C3N4 composite for improved visible light photocatalytic performance

ZnGaNO solid solution–C₃N₄ composite photocatalyst with visible light response was synthesized through polymerization of melamine in the presence of ZnGaNO solid solution. The composite photocatalyst was characterized by X-ray diffraction, high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FT-IR) spectroscopy, UV–vis diffuse reflection spectroscopy, X-ray photoelectron spectroscopy (XPS), Energy dispersed spectrometer (EDS) and BET surface area measurements. The activity of composite photocatalyst g-C₃N₄–ZnGaNO for photodegradation of methyl orange (MO) is higher than that of either single-phase g-C₃N₄ or ZnGaNO solid solution. The as-prepared composite photocatalyst exhibits an improved photocatalytic activity due to enhancement of electron–hole separations at the interface.     

Photocatalytic reduction of NO with NH3 using Si-doped TiO2 prepared by hydrothermal method

A series of Si-doped TiO2 (Si/TiO2) photocatalysts supported on woven glass fabric were prepared by hydrothermal method for photocatalytic reduction of NO with NH3. The photocatalytic activity tests were carried out in a continuous Pyrex reactor with the flow rate of 2000mL/min under UV irradiation (luminous flux: 1.1x10(4)lm, irradiated catalyst area: 160cm2). The photocatalysts were characterized by X-ray diffraction (XRD), BET, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectrophotometer, transmission electron microscopy (TEM), photoluminescence (PL) and temperature-programmed desorption (TPD). The experiment results showed that NO conversion on Si/TiO2 at 323K could exceed 60%, which was about 50% higher than that on Degussa P25 and pure TiO2. With the doping of Si, photocatalysts with smaller crystal size, larger surface area and larger pore volume were obtained. It was also found that Ti-O-Si bands were formed on the surface of Si/TiO2 and that the surface hydroxyl concentration was greatly increased. As a result, total acidity and NH3 chemisorption amount were enhanced for Si/TiO2 leading to its photocatalytic activity improvement.     

Photocatalytic properties of nano-structured TiO2-carbon films obtained by means of electrophoretic deposition

Recent studies have shown that the light-absorption and photocatalytic efficiencies of TiO2 can be improved by coupling TiO2 nano-particles with nonmetallic dopants, such as carbon. In this paper, we describe the electrophoretic preparation of a novel TiO2-carbon nano-composite photocatalyst on a glass indium thin oxide (ITO) substrate. The objective is to take better advantage of the (e-/h+) pair generated by photoexcitation of semiconducting TiO2 particles. The transfer of electrons (e-) into adjacent carbon nano-particles promotes reduction of oxygen to produce hydrogen peroxide (H2O2) which, in the presence of iron ions, can subsequently form hydroxyl radicals (*OH) via the Fenton reaction. At the same time, *OH is formed from water by the (h+) holes in the TiO2. Thus, the *OH oxidant is produced by two routes. The efficiency of this photolytic-Fenton process was tested with a model organic compound, Orange-II (OG-II) azo dye, which is employed in the textile industry.