铕掺杂的TiO2空心微球的制备及光催化性能

通过溶胶-凝胶法制备未掺杂和铕掺杂的TiO₂空心微球, 采用XRD、SEM、TEM、HRTEM、BET和XPS等技术对样品进行表征, 以亚甲基蓝的光催化降解为目标反应, 评价其光催化活性。结果表明, 钛酸四丁酯(TBOT)的加入量对微球的形貌影响较大, 当滴加1.5 mL的TBOT时, 可得结构清晰、分散性良好的TiO₂空心微球。XRD分析表明, 400℃煅烧的纳米TiO₂空心微球为锐钛矿, 掺铕可抑制TiO₂的晶相转变。光催化实验表明, 铕掺杂能显著提高TiO₂空心微球的活性。当铕掺量为0.7%时, 所得样品粒径和孔径最小, 比表面积最大, 光催化活性最高。     

分级介孔结构组成的ZnO微球及光催化性能

以硝酸锌、脲素及酒石酸为反应物, 采用水热法制备碱式碳酸锌前驱体微球, 通过煅烧前驱体制备了介孔氧化锌微球。通过扫描电子显微镜(SEM)可以观察到, 氧化锌微球的直径约为2~4 μm, 由大量厚度约为10 nm的介孔纳米片组装而成。X 射线衍射(XRD)和透射电镜(TEM)结果表明: ZnO微球为六方纤锌矿结构, 并结晶较好。比表面积测试(BET)表明ZnO微球为介孔材料, 孔径为20~50 nm, ZnO微球比表面积约为29.8 m²/g。以亚甲基蓝为目标降解物, 对介孔氧化锌微球进行了光催化降解实验。实验结果表明, 所合成的介孔ZnO微球对亚甲基蓝的光催化性能较好。     

Effects of Fe-doping on the photocatalytic activity of mesoporous TiO2 powders prepared by an ultrasonic method

Highly photoactive nanocrystalline mesoporous Fe-doped TiO(2) powders were prepared by the ultrasonic-induced hydrolysis reaction of tetrabutyl titanate (Ti(OC(4)H(9))(4)) in a ferric nitrate aqueous solution (pH 5) without using any templates or surfactants. The as-prepared samples were characterized by thermogravimetry and differential thermal analysis (TG-DTA), X-ray diffraction (XRD), N(2) adsorption-desorption measurements, UV-visible adsorbance spectra (UV-vis) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities were evaluated by the photocatalytic oxidation of acetone in air. The results showed that all the Fe-doped TiO(2) samples prepared by ultrasonic methods were mesoporous nanocrystalline. A small amount of Fe(3+) ions in TiO(2) powders could obviously enhance their photocatalytic activity. The photocatalytic activity of Fe-doped TiO(2) powders prepared by this method and calcined at 400 degrees C exceeded that of Degussa P25 (P25) by a factor of more than two times at an optimal atomic ratio of Fe to Ti of 0.25. The high activities of the Fe-doped TiO(2) powders could be attributed to the results of the synergetic effects of Fe-doping, large BET specific surface area and small crystallite size.     

含钛高炉渣催化剂的光催化活性

以攀钢含钛高炉废渣为原料,在不同温度下煅烧合成了钙钛矿型硫酸掺杂的含钛高炉渣催化剂(sulfuric acid-modified titanium-bearing blast furnace slag,STBBFS),研究了混晶结构和硫掺杂对含钛高炉渣光催化活性的影响,结果表明,含钛高炉渣催化剂具有钙钛矿/锐钛矿混晶结构,粉体的颗粒形状不规则,煅烧后粒径变大;在紫外区域具有很强的光吸收能力,STBBFS催化剂的光催化活性由Cr(Ⅵ)的还原率评价.煅烧温度为400℃时,STBBFS催化剂的表面存在含量较高的SO2-4和较高的CaTiO3/TiO2晶相比,具有较高的光催化活性,用500 W中压汞灯照射10 h,可将浓度为20 mg·L-1的六价铬废水完全降解.     

Effect of calcination temperature on the textural properties and photocatalytic activities of highly ordered cubic mesoporous WO3/TiO2 films

Highly organized cubic mesoporous WO3/TiO2 films were successfully prepared by evaporation-induced self-assembly (EISA) process, employing triblock copolymer as template. The characterization results by XRD, SEM, TEM, UV-Vis. spectrophotometry, and nitrogen adsorption-desorption isotherms reveal that the mesoporous films are made up of well-defined 3-D cubic (lm3m space group) mesoporous structure and nanocrystalline anatase frameworks with high surface area, uniform pore sizes and excellent optical transparency. Photocatalytic properties of the mesoporous WO3/TiO2 films in decomposing gaseous 2-propanol to CO2 were analyzed as a function of calcinations temperature. The highest photocatalytic activity was obtained for the films calcined at 450 degrees C, which possess an appropriate crystallinity and relevant ordering of mesoporous structure. It was found that that long-range ordering of mesopores is one of the important factors in determining the photocatalytic degradation of gaseous organics.     

铁铕共掺杂的TiO_2空心微球的制备及光催化活性

通过溶胶-凝胶法制备铁铕共掺杂的TiO_2(Fe~(3+)-Eu~(3+)/TiO_2)空心微球,采用XRD、TEM、BET和XPS等对样品进行表征,以亚甲基蓝(MB)的光催化降解为目标反应,评价其光催化活性。结果表明:SiO_2微球表面均匀地包覆了1层TiO_2,超声有利于提高SiO_2@TiO_2复合微球间的分散性,同时也发现煅烧前对SiO_2@TiO_2复合微球进行研磨处理后所得的Fe~(3+)-Eu~(3+)/TiO_2空心微球部分塌陷,而未研磨和煅烧后研磨所得Fe~(3+)-Eu~(3+)/TiO_2空心微球完整性较好。XRD和BET分析表明,Fe~(3+)-Eu~(3+)/TiO_2空心微球为锐钛矿且具有良好的介孔结构,铁铕共掺杂在TiO_2空心微球中产生协同作用,使Fe3+-Eu3+/TiO2空心微球的粒径进一步减小,比表面积增大。当Fe~(3+)的掺杂量为1.0%、Eu~(3+)的掺杂量为0.5%时,Fe~(3+)-Eu~(3+)/TiO_2空心微球的光催化活性最高。     

Effect of calcination temperatures on microstructures and photocatalytic activity of tungsten trioxide hollow microspheres

Tungsten trioxide hollow microspheres were prepared by immersing SrWO₄ microspheres in a concentrated HNO₃ solution, and then calcined at different temperatures. The prepared tungsten oxide samples were characterized by X–ray diffraction, X–ray photoelectron spectroscopy, Fourier transform infrared spectra, differential thermal analysis–thermogravimetry, UV–visible spectrophotometry, scanning electron microscopy, N₂ adsorption/desorption measurements. The photocatalytic activity of the samples was evaluated by photocatalytic decolorization of rhodamine B aqueous solution under visible-light irradiation. It was found that with increasing calcination temperatures, the average crystallite size and average pore size increased, on the contrary, Brunauer–Emmett–Teller-specific surface areas decreased. However, pore volume and porosity increased firstly, and then decreased. Increasing calcination temperatures resulted in the changes of surface morphology of hollow microspheres. The un-calcined and 300 °C-calcined samples showed higher photocatalytic activity than other samples. At 400 °C, the photocatalytic activity decreased greatly due to the decrease of specific surface areas. At 500 °C, the photocatalytic activity of the samples increased again due to the junction effect of two phases.     

煅烧温度对TiO2/硅藻土晶型结构与光催化性能的影响

以多孔非金属矿物硅藻土为载体, 钛酸四丁酯为前驱体, 采用溶胶–凝胶法制备TiO₂/硅藻土复合光催化材料。通过X射线衍射(XRD)、傅里叶红外光谱(FT-IR)、扫描电子显微镜(SEM)、紫外-可见分光光度计(UV-Vis spectroscopy)等方法对硅藻土及不同温度处理得到的复合样品的晶体结构、表面性能及形貌进行表征。结果表明: 载体硅藻土能够提高TiO₂的晶型转变温度, 并且使TiO₂纳米颗粒分散均匀, 有效抑制了团聚行为的发生。以10 mg/L的罗丹明B溶液为目标降解物, 250 W汞灯为光源, 研究不同热处理温度对TiO₂/硅藻土复合材料的光催化活性的影响。结果表明: 750℃煅烧2 h的样品光照120 min对罗丹明B的去除率接近100%, 与Degussa P25的去除率相当。此时样品中具有两种TiO₂晶型(A:R=9:1), 说明TiO₂的混晶效应能够有效地抑制光生电子-空穴复合, 使样品具有比单一锐钛矿型TiO₂更好的光催化性能。     

Zn-Mn-O heterostructures: Study on preparation, magnetic and photocatalytic properties

In this work, a method composed of electrospinning technique and subsequent calcinations was used to fabricate Zn-Mn-O heterostructures with unique morphologies and microspheres composed of ZnO micro/nanofibers successfully. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were applied to characterize the morphology and the crystallinity of the samples. The mechanism was proposed based on the formation process of ZnO materials calcined under different temperatures. The photocatalytic activity of all the Zn-Mn-O heterostructures was systematically investigated in decomposing Methylene Blue (MB) under UV lamp irradiation. In addition, the magnetic properties of Zn-Mn-O heterostructures were evaluated by vibrating sample magnetometer (VSM), and it was observed that all the Zn-Mn-O heterostructures exhibit slight ferromagnetic properties which will contribute to the recycle of the catalysts.     

Effect of filler types and calcination temperature on the microstructure and the nitric oxide photocatalytic activity of composite titanium dioxide films

The composite titanium dioxide (TiO(2)) films coating on the woven glass fabric were prepared by a modified sol-gel process, using pre-calcinated TiO(2) nanoparticle or silica gel as filler. The characterized physicochemical properties of the prepared catalyst films showed that the specific surface area, the microstructure and the crystal structure of the catalysts were greatly affected by the fillers and the calcination temperature. The physicochemical properties of composite films and the photocatalytic activity of nitric oxide (NO) show that the pre-calcinated TiO(2) nanoparticle is more favorable than silica gel as filler. The pre-calcinated TiO(2) nanoparticle filler can increase the photocatalytic activities of the catalysts by increasing the specific surface area, introducing a bimodal mesoporous structure, and creating a polymorphous crystal structure. And the TiO(2)-TiO(2) film calcinated at 400 degrees C exhibits the highest photocatalytic activity for NO oxidation and is more active than Degussa P25.     

ZnS微球的水热/溶剂热法合成及其光催化性能研究

采用水热/溶剂热法, 以Zn(Ac)₂·2H₂O和 CH₄N₂S为反应物合成ZnS微球。对ZnS微球进行X射线衍射(XRD)、扫描电镜(SEM)及紫外可见漫反射光谱等表征。结果表明, 合成的ZnS微球为立方闪锌矿型晶体结构, 由ZnS纳米粒子自组装而成。在降解苯酚水溶液的光催化研究中, 以乙二醇-水为溶剂合成的ZnS光催化活性明显优于其他溶剂体系合成的ZnS, 循环使用3次仍保持较高的活性。ZnS微球光催化性能的提高可归结为以下三方面的协同作用: 较小的禁带宽度(3.39 eV)有利于吸收光子, 较完整的晶体结构使催化剂活性分子数增多和较大的比表面积(19.4 m²/g)有利于反应液与催化剂的充分接触。ZnS微球降解苯酚的中间产物为乙二酸、顺丁烯二酸和极少量的对苯二酚。     

Preparation of Fe3+-doped TiO2 catalysts by controlled hydrolysis of titanium alkoxide and study on their photocatalytic activity for methyl orange degradation

Fe3+-doped TiO2 (Fe-TiO2) porous microspheres were prepared by controlled hydrolysis of Ti(OC4H9)4 with water generated "in situ" via an esterification reaction between acetic acid and ethanol, followed by hydrothermal treatment. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic absorption flame emission spectroscopy (AAS), electron paramagnetic resonance (EPR) spectrum, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), and nitrogen adsorption-desorption methods. All of the undoped TiO2 and Fe-TiO2 samples exclusively consist of primary anatase crystallites, which further form porous microspheres with diameters ranging from 150 to 500 nm. The photocatalytic activity of Fe-TiO2 catalysts was evaluated from the photodegradation of methyl orange (MO) aqueous solution both under UV and visible light irradiation. Fe3+ doping effectively improves the photocatalytic activity under both UV light irradiation and visible light irradiation with an optimal doping concentration of 0.1 and 0.2%, respectively. The photocatalytic mechanisms of Fe-TiO2 catalysts were tentatively discussed.     

Synthesis of mesoporous BiOBr 3D microspheres and their photodecomposition for toluene

In this article, a facile solvothermal method was introduced to synthesize mesoporous BiOBr microspheres with Bi(NO₃)₃ as Bi source. The synthesized catalysts were characterized by XRD, SEM, TEM, XPS, UV-vis, TG-DTA, and N₂-adsorption-desorption, and their photoactivity was evaluated by gaseous toluene both under UV and UV-vis irradiation with Degussa TiO₂ P₂₅ as reference. The prepared BiOBr catalysts were of pure tetragonal phase and its band gap energy was calculated to be about 2.64 eV. Comparing with P₂₅, BiOBr showed promoted photocatalytic activity under UV-vis irradiation, during which more than 90% of toluene was eliminated after 5 h irradiation. Kinetic analysis further demonstrated the enhanced activity of BiOBr under UV-vis irradiation and the reaction rate constant k of BiOBr was nearly 2 times higher than that of P₂₅. The superior activity of BiOBr under UV-vis irradiation can be attributed to its hierarchical structure and suitable band gap energy. Moreover, the reacted intermediates under different light source were identified by GC-MS. Fifteen main intermediates were identified and a tentative pathway of toluene degradation by BiOBr was proposed.     

Synergistic effects of hollow structure and surface fluorination on the photocatalytic activity of titania

To study the synergistic effects of hollow structure and surface fluorination on the photoactivity of TiO₂, TiO₂ hollow microspheres were synthesized by a hydrolysis–precipitate method using sulfonated polystyrene (PS) as templates and tetrabutylorthotitanate (TBOT) as precursor, and then calcined at 500 °C for 2 h. The calcined samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N₂ sorption. Photocatalytic activity was evaluated using reactive brilliant red X3B, an anionic organic dye, as a model pollutant in water. The results show that the photocatalytic activity of TiO₂ hollow microspheres is significantly higher than that of TiO₂ nanoparticles prepared in the same experimental conditions. At pH 7 and 3, the apparent rate constants of the former exceed that of the latter by a factor of 3.38 and 3.15, respectively. After surface fluorination at pH 3, the photoactivity of hollow microspheres and nanoparticles further increases for another 1.61 and 2.19 times, respectively. The synergistic effect of surface fluorination and hollow structure can also be used to prepare other highly efficient photocatalyst.     

Effects of structure of anodic TiO(2) nanotube arrays on photocatalytic activity for the degradation of 2,3-dichlorophenol in aqueous solution

In this study titanium dioxide nanotube (TNT) arrays were prepared by an anodic oxidation process with post-calcination. The morphology and structure of the TNT films were studied by field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of the TNT films was evaluated in terms of the degradation of 2,3-dichlorophenol in aqueous solution under UV light irradiation. The effects of the nanotube structure including tube length and tube wall thickness, and crystallinity on the photocatalytic activity were investigated in detail. The results showed that the large specific surface area, high pore volume, thin tube wall, and optimal tube length would be important factors to achieve the good performance of TNT films. Moreover, the TNT films calcined at 500 degrees C for 1h with the higher degree of crystallinity exhibited the higher photocatalytic activity than other TNT films calcined at 300 and 800 degrees C. Consequently, these results indicate that the optimization of TiO(2) nanotube structures is critical to achieve the high performance of photocatalytic reaction.     

Facile synthesis and enhanced photocatalytic activity of hierarchical porous ZnO microspheres

In this paper, hierarchical porous ZnO microspheres were successfully synthesized by calcining the microspheric zinc hydroxide carbonate (ZHC) precursor, which were the precipitate products of a hydrothermal reaction by zinc nitrate hexahydrate and urea in the presence of trisodium citrate. The as-prepared ZnO microspheres with diameters of 4-5 μm were assembled by numerous porous nanosheets which had the uniform thickness of about 10 nm. The photocatalytic activity of the ZnO microspheres was evaluated by photodegradation reaction of methylene blue (MB). The as-prepared ZnO microspheres exhibited a significantly enhanced photocatalytic activity than commercial ZnO and TiO₂. This was mainly attributed to the larger specific surface area and stability against aggregation.     

Aqueous Cr(VI) photo-reduction catalyzed by TiO2 and sulfated TiO2

TiO(2) and sulfated TiO(2) (SO(4)(2-)/TiO(2)) catalysts with different textural properties were prepared under different calcination temperatures and the photo-reduction of Cr(VI) to Cr(III) catalyzed by these catalysts was investigated. For the photocatalytic reduction of Cr(VI), the photocatalytic activities of the TiO(2) samples were found to be strongly dependent of the calcination temperature and TiO(2) calcined at 400 degrees C showed a higher catalytic activity compared to other TiO(2) catalysts. In contrast, sulfation of TiO(2) stabilized the catalytic activities of SO(4)(2-)/TiO(2) catalysts. At low calcination temperature, SO(4)(2-)/TiO(2) catalysts exhibited catalytic activities almost comparable with that of TiO(2) and the catalytic activities of SO(4)(2-)/TiO(2) catalysts were markedly higher than TiO(2) under high calcination temperature. In addition, the removal of surface SO(4)(2-) of SO(4)(2-)/TiO(2) catalyst led to a marked decrease of the catalytic activity for Cr(VI) photo-reduction, suggesting that the presence of surface SO(4)(2-) provided an acid environment over the catalyst surface and favored the photo-reduction of Cr(VI).     

Self-assembly and photocatalysis of mesoporous TiO2 nanocrystal clusters

Mesoporous nanocrystal clusters of anatase TiO₂ with large surface area and enhanced photocatalytic activity have been successfully synthesized. The synthesis involves the self-assembly of hydrophobic TiO₂ nanocrystals into submicron clusters, coating of these clusters with a silica layer, thermal treatment to remove organic ligands and improve the crystallinity of the clusters, and finally removing silica to expose the mesoporous catalysts. With the help of the silica coating, the clusters not only maintain their small grain size but also keep their mesoporous structure after calcination at high temperatures (with BET surface area as high as 277 m²/g). The etching of SiO₂ also results in the clusters having high dispersity in water. We have been able to identify the optimal calcination temperature to produce TiO₂ nanocrystal clusters that possess both high crystallinity and large surface area, and therefore show excellent catalytic efficiency in the decomposition of organic molecules under illumination by UV light. Convenient doping with nitrogen converts these nanocrystal clusters into active photocatalysts in both visible light and natural sunlight. The strategy of forming well-defined mesoporous clusters using nanocrystals promises a versatile and useful method for designing photocatalysts with enhanced activity and stability.     

Controllable synthesis of uniformly distributed hollow rutile TiO2 hierarchical microspheres and their improved photocatalysis

We reported the controllable synthesis of uniformly distributed hierarchical hollow microspheres composed of rutile TiO₂ nanorods as building blocks, prepared by a hydrothermal method without employing any templates/substrates or surfactants. The homogenous hollow microspheres were obtained by optimizing the experimental conditions including hydrothermal temperatures and tetrabutyl titanate (TBOT) concentrations. A detailed formation mechanism was also proposed. The samples were analyzed by Brunauer–Emmett–Teller (BET) specific surface area analysis and ultraviolet–visible (UV–Vis) diffuse reflectance spectra (DRS). The photocatalytic results for methylene orange (MO) degradation showed that the hollow hierarchical microspheres exhibited the best photocatalytic activity among the as-synthesized products. Further optimum photocatalytic conditions were determined to study the degradation rate, decolorization and TOC (total organic carbon) removal efficiencies, and reaction kinetics in detail. Under optimum conditions, the contrastive photocatalytic experiments indicated that the photocatalytic activity was enhanced markedly when assembling the single-crystal rutile TiO₂ nanorods into hollow hierarchical microstructures.     

Complete oxidation of formaldehyde at ambient temperature over supported Pt/Fe2O3 catalysts prepared by colloid-deposition method

The catalytic properties of iron oxide supported platinum catalysts (Pt/Fe(2)O(3)), prepared by a colloid deposition route, were investigated for the complete oxidation of formaldehyde. It is found that all the Pt/Fe(2)O(3) catalysts calcined at different temperatures (200-500°C) were active for the oxidation of formaldehyde. Among them, the catalysts calcined at lower temperatures (i.e., 200 and 300°C) exhibited relatively high catalytic activity and stability, which could completely oxidize HCHO even at room temperature. Based on a variety of physical-chemical characterization results, it is proposed that the presence of suitable interaction between Pt particles and iron oxide supports, which is mainly in the form of Pt-O-Fe bonds, should play a positive role in determining the catalytic activity and stability of the supported Pt/Fe(2)O(3) catalysts.