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.     

由纳米管和纳米颗粒构成的TiO2膜的制备与机理研究

采用聚苯乙烯小球修饰Ti片表面,并进行阳极氧化,制备出一种由纳米颗粒和纳米管构成的TiO₂膜．通过数值模拟,分析了氧化表面附近的局部电场分布对TiO₂膜形貌的影响．结果表明,覆盖物增强了局部电场,从而加快了O^2-与Ti的反应速率,有利于TiO₂的生长;与此同时,[TiF₆]^6-的扩散受到阻碍,使得TiO₂的溶解速率减慢．可见,覆盖物打破了TiO₂纳米管形成的平衡条件,导致纳米颗粒的生成．此外,通过X射线衍射和Raman光谱的测试分析发现,所制备的TiO₂为锐钛矿结构.     

臭氧修饰(001)晶面TiO2纳米片及其光催化降解甲苯研究

本文系统研究了臭氧修饰对(001)主导晶面锐钛矿型TiO₂光催化剂降解甲苯性能的影响. 利用自行搭建的光催化VOCs降解装置对催化剂光降解甲苯的性能进行了测试. 通过多种表征手段,结合原位DRIFTS和DFT计算研究了臭氧表面修饰及甲苯吸附和降解机理. 结果表明,用臭氧进行表面修饰可以显著提高(001)主导晶面TiO₂光催化降解甲苯的性能. (001)晶面上丰富的5c-Ti不饱和配位是臭氧分子的吸附位点,其解离后形成的Ti-O键与H₂O分子结合,在表面生成大量孤立的Ti_5c-OH. Ti_5c-OH 是甲苯分子的吸附位,它的形成显著提高了对甲苯分子的吸附能力. 在光照下Ti_5c-OH与光生空穴结合能形成·OH自由基. 通过臭氧解离产生的O₂也可以与光生电子结合形成超氧自由基. 这些具有强氧化性活性自由基的形成促进了对气相甲苯的光催化降解速率.     

铈和磷钨酸共掺杂纳米二氧化钛中空纤维的制备及其光催化活性

以棉花纤维为模板,以钛酸四正丁酯、硝酸铈铵和磷钨酸为原料采用模板法制备了一系列铈和磷钨酸共掺杂的、具有中空纤维结构的TiO₂光催化材料, 利用扫描电子显微镜、X射线衍射、BET和紫外-可见光谱等技术对其形貌、晶体结构及表面结构、光吸收特性等进行了表征. 以苯酚溶液的光催化降解为模型反应,考察了不同掺杂量的样品在紫外和可见光下的光催化性能. 结果表明,用模板法制备的TiO₂纤维材料具有中空结构,共掺杂的TiO₂纤维在紫外和可见光条件下较纯TiO₂纤维和单掺杂TiO₂纤维对苯酚溶液具有更好的光催化降解效果, 且铈和磷钨酸的掺杂量显著影响该纤维材料的催化性能;当铈掺杂量为0.3mol%和磷钨酸掺杂量为2mol%,在500 oC焙烧2 h所得中空纤维材料的催化性能最佳,4 h即可使苯酚溶液的降解率达98.5%;重复使用4次仍可使苯酚溶液的降解率保持在87%以上,且该催化剂材料易于离心分离去除.     

FeTPP-Cr-TiO2微球的制备及其可见光催化性能

通过四苯基铁卟啉敏化Cr掺杂TiO₂微球成功合成了一种复合改性可见光催化剂FeTPP-Cr-TiO₂.利用XRD、FT-IR、SEM、XPS、UV-Vis和N₂吸附-脱附等温线等技术对其结构和形貌进行了表征.以亚甲基蓝为目标降解物,在150 W氙灯的辐照下,考察了其可见光催化活性.结果表明FeTPP-Cr-TiO₂呈锐钛矿相,表面积为74.7 m²/g.与Cr-TiO₂和FeTPP-TiO₂相比,FeTPP-Cr-TiO₂表现出很好的可见光降解性能.以三种喹诺酮类抗生素（洛美沙星、诺氟沙星和氧氟沙星）为实验对象,考察了FeTPP-Cr-TiO₂降解水体中抗生素的可行性,对三种抗生素均有很高的降解率,降解过程符合一级动力学模型,反应动力学常数分别为3.02×10^-2、2.81×10^-2和3.86×10^-2min^-1,半衰期为22.9、24.6及17.9 min.     

硫和银共掺杂介孔TiO2的制备、表征及其对染料的光催化降解活性

以P123为模板,以钛酸四正丁酯、硝酸银和硫脲为原料采用模板法制备了一系列硫和银共掺杂介孔TiO₂光催化材料．利用SEM、XRD、BET和紫外-可见光谱等技术对其形貌、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,考察了不同掺杂量的样品在紫外和可见光下的光催化性能．结果表明,用模板法制备的共掺杂介孔TiO₂光催化材料在紫外和可见光条件下较纯介孔TiO₂和单掺杂介孔TiO₂对甲基橙溶液具有更好的光催化降解效果, 且硫和银的掺杂量及样品焙烧温度显著影响该材料的催化性能．当硫掺杂量为2mol%和银掺杂量为1mol%,在500 oC 焙烧2 h所得光催化材料的催化性能最佳,4 h即可使甲基橙的降解率达98.8%,重复使用4次仍可使甲基橙的降解率保持在87.5%以上     

甲醇分子在金红石TiO2(110)和锐钛矿TiO2(001)表面吸附和反应的活性位点

通过高分辨的扫描隧道显微术研究并比较了金红石型TiO₂(110)-(1×1)和锐钛矿型TiO₂(001)-(1×4)两种表面的活性位点． 在金红石型TiO₂(110)-(1×1)表面, 观察到氧空位缺陷是O₂和CO₂分子的活性吸附位点,而五配位的Ti原子是水分子和甲醇分子的光催化反应活性位点．在锐钛矿型TiO₂(001)-(1×4)表面,观察到完全氧化的表面,Ti原子更可能是六配位的,H₂O和O₂分子均不易在这些Ti原子上吸附．经还原后表面出现富Ti的缺陷位点, 这些缺陷位点对H₂O和O₂分子表现出明显的活性． 锐钛矿型TiO₂(001)-(1×4)表面的吸附和反应活性并不具有很高的活性,某种程度上其表现出的活性似乎低于金红石型TiO₂(110)-(1×1)表面．     

Ag-Cu纳米颗粒修饰的N掺杂TiO2纳米棒阵列及其高效光催化CO2还原应用

本文采用微纳加工方法制备了负载高密度Ag-Cu纳米颗粒的N掺杂TiO₂纳米棒阵列样品. 通过TiO₂的N掺杂,可将其吸光范围调控至与Ag纳米颗粒的等离激元吸收频率相匹配的波段,从而实现复合材料中肖特基结与共振能量转移过程的协同作用. 与此同时,Cu纳米颗粒可以为CO₂还原提供活性位点. 在全谱光照射下,复合样品光催化CO₂还原的活性显著提高,CH₄生成速率可达720 μmol·g^-1·h^-1.     

二氧化钛纳米晶/石墨烯复合物的制备及其光催化性能 (cited: 1)

以氧化石墨和TiO₂溶胶为前驱物,结合絮凝与水热技术制备了TiO₂纳米晶/石墨烯复合物,表征了产物的结构、形貌、孔隙率、光谱吸收性质. 结果表明：TiO₂纳米晶的存在一定程度上阻止了石墨烯片层的重组,TiO₂纳米晶/石墨烯复合物较单纯TiO₂材料具有更强的吸光性能、对亚甲基蓝分子更强的吸附性能以及更高的电荷分离效率. 在紫外光和太阳光下,TiO₂纳米晶/石墨烯复合物对亚甲基蓝的光催化降解效率均高于P25和纯TiO₂.     

镧掺杂介孔TiO2光催化剂的制备、表征及其光催化性能

以钛酸四正丁酯和硝酸镧为原料, 以P123为模板剂,采用模板法合成了La掺杂型介孔TiO₂光催化剂, 借助TGA-DSC、BET、XRD及UV-Vis等测试手段对样品进行了表征,并以苯酚为模型污染物考察了镧掺杂量对样品光催化活性的影响．结果表明: La掺杂介孔TiO₂光催化剂孔径分布较均匀(～10 nm),比表面积可达165 m²/g．与纯介孔TiO₂相比,经掺杂改性后的样品在紫外光区及可见光区的吸收显著增强,对光具有更高的利用率,La掺杂可显著提高介孔TiO₂的光催化活性.     

Synthesis of fluorinated TiO2 hollow microspheres and their photocatalytic activity under visible light

Fluorinated TiO₂ hollow microspheres with three-dimensional hierarchical architecture were prepared by solvothermally treatment using solid microspheres as precursor. The obtained solid and hollow TiO₂ microspheres were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectrum (DRS) and photoluminescence (PL) spectra. The photocatalytic activity of as-prepared solid and hollow TiO₂ microspheres was determined by degradation of methyl orange (MO) under visible light irradiation. The results showed that the surface fluorination, the existence of accessible mesopores channels, and the increased light harvesting abilities could remarkably improve the photocatalytic activity of TiO₂ hollow microspheres.     

Enhanced photocatalytic activity of graphene–TiO2 composite under visible light irradiation

Novel graphene–TiO₂ (GR–TiO₂) composite photocatalysts were synthesized by hydrothermal method. During the hydrothermal process, both the reduction of graphene oxide and loading of TiO₂ nanoparticles on graphene were achieved. The structure, surface morphology, chemical composition and optical properties of composites were studied using XRD, TEM, XPS, DRS and PL spectroscopy. The absorption edge of TiO₂ shifted to visible-light region with increasing amount of graphene in the composite samples. The photocatalytic degradation of methyl orange (MO) was carried out using graphene–TiO₂ composite catalysts in order to study the photocatalytic efficiency. The results showed that GR–TiO₂ composites can efficiently photodegrade MO, showing an enhanced photocatalytic activity over pure TiO₂ under visible-light irradiation. The enhanced photocatalytic activity of the composite catalysts might be attributed to great adsorptivity of dyes, extended light absorption range and efficient charge separation due to giant π-conjugation system and two-dimensional planar structure of graphene.     

Preparation, characterization and visible-light photocatalytic activity of AgI/AgCl/TiO2

In this paper, a novel composite photocatalyst AgI/AgCl/TiO₂ was prepared by ion exchange method and characterized by XRD, SEM and UV-Vis spectrometry. The as-prepared AgI/AgCl/TiO₂ composites show much higher photocatalytic activity than AgCl/TiO₂ and AgI/TiO₂ under visible-light irradiation (λ > 400 nm) in the process of methyl orange (MO) degradation. When the molar percentage of AgI to initial AgCl is 20% (sample SE-20%), the maximal degradation efficiency of MO has reached 85.8% after irradiation for 120 min. The enhancement of photocatalytic activity of the composite photocatalyst AgI/AgCl/TiO₂ will be attributed to its good absorption in the visible-light region, especially low recombination rate of the electron-hole pairs based on the photoluminescence (PL) spectra investigation of AgI/AgCl/TiO₂ and the matching band structures of AgI, AgCl and TiO₂. The detection of reactive species by radical scavengers displays that O₂⁻ and H₂O₂ are the main reactive species for the degradation of MO under visible-light irradiation. Moreover, PL analysis by using terephthalic acid (TA) as a probe molecule further reveals that OH can be negligible for the degradation of MO.     

Photocatalytic activity enhancement of Dy-doped TiO2 nanoparticles hybrid with TiO2 (B) nanobelts under UV and fluorescence irradiation

The main drawbacks of anatase titanium dioxide (TiO₂) nanoparticles for being used as a photocatalyst are due to the rapid charge recombination of the electron-hole pairs and the wide band gap energy, limiting its photocatalysis application. To enhance photocatalytic activity, structure modification was performed here. Heterogeneous nanostructure of Dy-doped TiO₂ nanoparticles hybrid with Monoclinic TiO₂ nanobelts (Dy/TNBs) was fabricated via hydrothermal method. Annealing temperature was varied to investigate its effect on phase composition and morphology of the as-prepared TiO₂ catalyst. Phase composition and morphology were studied by XRD and SEM, respectively. The effect of amount of catalyst loaded on the degradation efficiency of methylene blue (MB) dye in aqueous solution under UV and fluorescence illumination was investigated. The results showed that pure monoclinic TiO₂ nanobelts (TNBs) was achieved at 450 °C. Enhanced photocatalytic activity under both UV and fluorescence irradiation was found on Dy/TNB samples. The optimum Dy dosage providing the highest MB degradation rates under both irradiation sources was 0.1 mol%.     

Design and fabrication of a TiO2/nano-silicon composite visible light photocatalyst

Nano-silicon (nc-Si) was utilized as the charges generator to promote the photocatalytic and super-hydrophilic reactivity of TiO₂ film under visible light irradiation. The photocatalytic ability of TiO₂/nc-Si composite photocatalyst was evaluated by a set of experiments to photodecompose 100 ppm methylene blue (MB) in aqueous solution. And the super-hydrophilic property was characterized by measuring the water droplet contacts angle, under visible light irradiation in atmospheric air and at room temperature. Under 100 mW/cm² visible light irradiation, the droplet contact angles were reduced to 0° within 4 h with nc-Si charge generator. Additionally, the rate constant of MB photo-degradation was promoted 6.6 times.     

Hydrothermal synthesis of C-doped Zn3(OH)2V2O7 nanorods and their photocatalytic properties under visible light illumination

A visible light-driven photocatalyst, C-doped Zn₃(OH)₂V₂O₇, prepared by a hydrothermal method was studied. The as-prepared catalyst was characterized by SEM, XRD, DRS, and XPS, and exhibited efficient photocatalytic activity in the degradation of methylene blue (MB) under visible-light irradiation. Besides decoloring, the decomposition of MB was also observed, further demonstrating the performance of the photocatalyst. The carbon existing on the surface of Zn₃(OH)₂V₂O₇ nanorods was free and in carbide form. Dye degradation followed first-order kinetics, and was explained on the basis of the Langmuir-Hinshelwood mechanism.     

Effect of surface ethoxy groups on photoactivity of TiO2 nanocrystals

TiO₂ nanocrystals modified by ethoxy groups were prepared by a facile nonhydrolytic solvothermal method and characterized by XRD, TEM, TG-DTA and XPS, which showed an enhanced visible-light photocatalytic activity on the degradation of Rhodamine B compared with TiO₂ modified by benzyloxy groups and the “naked” TiO₂. The adsorption and degradation pathway of Rhodamine B on TiO₂ modified by ethoxy groups were also investigated. The zeta-potential (ζ) results showed that the TiO₂ modified by ethoxy groups had high negative surface charge, which incited the positive -N(Et)₂ group of RhB absorbing on the TiO₂ surface and preferably led the N-dealkylation pathway under visible light irradiation.     

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.     

EPR study of the illumination effect on properties of paramagnetic centers in nitrogen-doped TiO<Subscript>2</Subscript> active in visible light photocatalysis

An electron paramagnetic resonance study of nitrogen-doped TiO₂ samples has been carried out in the dark and under illumination with light at different wavelengths. N^· and NO^· paramagnetic species were detected in the samples and their dynamics under illumination of TiO₂ was investigated. Photosensitivity of the nitrogen-doped TiO₂ and its photocatalytic activity under visible-light irradiation increases through the creation of additional levels in the band gap of TiO₂ caused by doping.     

Synthesis of samarium- and nitrogen-co-doped TiO2 by modified hydrothermal method and its photocatalytic performance for the degradation of 4-chlorophenol

Sm- and nitrogen-co-doped TiO₂ (Sm-N-TiO₂) catalysts were prepared via the modified hydrothermal method using tetrabutyl titanate as the precursor and calcination at 200 °C. The microstructure of the sample was characterized by X-ray diffraction (XRD), ultraviolet-visible diffuse reflection spectroscopy (UV-vis-DRS), Fourier transform infrared (FTIR) spectra and X-ray photoelectron spectroscopy (XPS). The average particle size was ca. 16.0 nm as calculated from XRD patterns. Sm-N-TiO₂ nanocrystalline showed strong visible-light response and high photocatalytic activity for 4-chlorophenol degradation under irradiation by visible-light (400-500 nm). The high visible-light photocatalytic activity of the obtained Sm-N-TiO₂ might result from the incorporation of nitrogen atoms in TiO₂, which extended the spectral response to the visible region, and Sm₂O₃ facilitated the excited electron transfer and hence suppressed efficiently the recombination of photoproduced electron-hole.