Atomic layer deposition of TiO2−xNx thin films for photocatalytic applications

Titanium dioxide (TiO₂) is recognized as the most efficient photocatalytic material, but due to its large band gap energy it can only be excited by UV irradiation. Doping TiO₂ with nitrogen is a promising modification method for the utilization of visible light in photocatalysis. In this work, nitrogen-doped TiO₂ films were grown by atomic layer deposition (ALD) using TiCl₄, NH₃ and water as precursors. All growth experiments were done at 500 °C. The films were characterized by XRD, XPS, SEM and UV–vis spectrometry. The influence of nitrogen doping on the photocatalytic activity of the films in the UV and visible light was evaluated by the degradation of a thin layer of stearic acid and by linear sweep voltammetry. Light-induced superhydrophilicity of the films was also studied. It was found that the films could be excited by visible light, but they also suffered from increased recombination.     

Atomic layer deposition of TiO2 nanotubes and its improved electrostatic capacitance

Titanium dioxide (TiO₂) nanotubes are fabricated into anodic aluminum oxide (AAO) membrane via atomic layer deposition (ALD). For the ALD of TiO₂, gaseous precursors, titanium (IV) isopropoxide and water are sequentially applied and chemically reacted with each other. A thickness of nanotubes is precisely controlled by the applied cycle numbers of ALD and the morphology of nanostructures is investigated by SEM and TEM. The amorphous property of TiO₂ nanostructures is revealed by XRD and the composition of nanotubes is measured by TEM–EDX. The impurity contents and binding structure of the nanostructures are analyzed by XPS. The electrostatic capacitance of TiO₂ nanotubes into AAO is 480 μF/cm² and it is about 3 times higher compared with AAO membrane (172 μF/cm²).     

Atomic layer deposition of metal-oxide thin films on cellulose fibers

Abstract

Atomic layer deposition (ALD) is a vapor-phase technique capable of producing inorganic thin films with precise control over the thickness of the film. The ALD method offers high precision in the design of advanced 3D nanostructures. In this article, silica and alumina thin films have been grown over fibers of cellulose by the ALD process. The morphology and the chemical composition of the fabricated thin films are characterized, as well as their thermal durability through elevated temperatures. Moreover, XPS is used to confirm the phases of the alumina nanofilms and to further understand the deposition process on the cellulose microfibers.     

Preparation and solar-light photocatalytic activity of TiO2 composites: TiO2/kaolin,TiO2/diatomite,and TiO2/zeolite

Three TiO₂ loaded composites, TiO₂/kaolin, TiO₂/diatomite, and TiO₂/zeolite, were prepared in order to improve the solar-light photocatalytic activity of TiO₂. The results showed that the photocatalytic activity could obviously be enhanced by loading appropriate amount of inorganic mineral materials. Meanwhile, TiO₂ content, heat-treatment temperature and heat-treatment time on the photocatalytic activity were reviewed. Otherwise, the effect of solar light irradiation time and dye concentration on the photocatalytic degradation of Acid Red B was investigated. Furthermore, the degradation mechanism and adsorption process were also discussed.     

负载型混晶纳米TiO_2/硅藻土复合材料的制备及其光催化性能

选用市售硅藻土作为载体,采用液相沉积法制备了负载型混晶纳米TiO2/硅藻土复合材料;采用扫描电镜、X射线衍射仪及红外光谱仪分析了复合材料的表面形貌和晶体结构;基于甲醛光催化降解实验考察了不同组成的负载型TiO2/硅藻土复合材料的光催化性能.结果表明,TiO2负载量为33.3%(TiO2与硅藻土的质量比为1∶2)的复合材料对甲醛光催化降解具有最佳催化活性.     

Preparation, characterization and photocatalytic activity of metalloporphyrins-modified TiO2 composites

Three new Cu(II), Zn(II), Co(II) 5,15-di (4-hydroxyphenyl)-10, 20-diphenyl-porphyrin (CuDHPP, ZnDHPP, CoDHPP) and the corresponding metalloporphyrins–TiO₂ photocatalysts CuDHPP–TiO₂, ZnDHPP–TiO₂, CoDHPP–TiO₂ were synthesized and characterized by SEM, XRD, FT-IR, and DRS. The results revealed that the metalloporphyrins impregnated onto the surface of TiO₂ did not change the phase composition and particle sizes of TiO₂ samples, but increased the photocatalytic efficiency. In addition, photoluminescence study showed that the three photocatalysts could successfully increase the separation efficiency of the photoinduced electron and hole. The photodegrading 4-NP experiments indicated that the three photocatalysts greatly enhanced the photocatalytic activity of bare TiO₂, and the photocatalytic activity of CuDHPP–TiO₂ was the highest. Moreover, the possible mechanism for the photodegradation of 4-NP was also proposed.     

Enhanced photocatalytic activity in composites of TiO2 nanotubes and CdS nanoparticles

A new composite consisting of TiO(2) nanotubes and CdS nanoparticles, where CdS particles bind covalently to the titania surface through a bifunctional organic linker, was successfully fabricated; this titania nanotube-based composite shows enhanced photocatalytic activity under visible-light irradiation.     

H4SiW12O40/TiO2/SiO2复合光催化剂的制备及性能研究

溶胶-凝胶法制备了TiO2/S iO2光催化剂,利用所得TiO2/S iO2光催化剂为基体,浸渍烧结法制备了H4S iW12O40/TiO2/S iO2表面负载修饰型复合光催化剂。TG-DSC、XRD、SEM、BET对催化剂的物化结构进行了表征,分析了TiO2和H4S iW12O40催化活性组分在S iO2载体表面上的键联机理。光催化性能测试是以低浓度酸性品红染料的水溶液为降解目标物,试验结果表明H4S iW12O40的负载修饰可以改进TiO2/S iO2光催化剂的催化活性,酸性品红的降解效率最高可以增加45%。     

石墨烯/电气石/二氧化钛复合材料的制备及其光催化降解异丙醇性能

光催化是一种理想的应对全球能源短缺和环境污染问题的绿色化学技术,可以实现有机物降解、水分解和二氧化碳光还原等.光催化反应效率受诸多因素影响,其中光生载流子(电子和空穴)的分离和传输具有至关重要的作用.以往研究表明,构筑多元复合光催化材料体系有利于光生电子和空穴有效分离和传递,促进催化剂表面的还原和氧化反应,从而提高其光催化效率.基于以上考虑,我们提出了一种新型的石墨烯/电气石/TiO2三元复合光催化材料体系,其中TiO2因其价格低廉、无毒和抗光腐蚀等优点而被广泛用作光催化材料;石墨烯(G)拥有独特的二维结构、高的电子迁移率、大的比表面积,是一种优异的催化剂载体;电气石(T)的一个重要性质是表面存在自发极化的静电场,该静电场将会影响光激发载流子的分离、传递和光催化反应过程.利用水热法合成了不同成分的石墨烯/电气石/TiO2三元复合材料体系.为了对比研究石墨烯表面电荷性质的影响,其中一组的石墨烯(氧化石墨)为直接采用改良的Hummers法所制备,其表面带负电;另一组的石墨烯经聚二烯丙基二甲基氯化铵(PDDA)修饰,使其表面带正电.X射线衍射结果显示,三元复合材料中TiO2为锐钛矿相,其结晶性没有因为与石墨烯和电气石的复合而受到影响.扫描和透射电子显微分析表明,TiO2的平均颗粒大小为15 nm左右,并且与石墨烯和电气石均匀复合.傅里叶变换红外光谱和zeta电位表征分析证实,PDDA可以有效地对石墨烯进行功能化改性,使其表面带正电.紫外-可见分光光谱显示,石墨烯/电气石/TiO2三元复合材料与TiO2的吸收带边一致,复合材料中石墨烯和电气石并没有改变TiO2的光吸收特征.光催化降解异丙醇实验表明,石墨烯/电气石/TiO2三元复合材料优于单纯的TiO2、石墨烯/TiO2以及电气石/TiO2二元复合材料,当石墨烯和电气石的质量百分比分别为0.5%和5%时,三元复合材料降解异丙醇产生丙酮的速率达到最高(223μmol/h).特别值得指出的是,由表面带负电的石墨烯组成的复合材料比由带正电荷的PDDA-石墨烯组成的复合材料具有更高的光催化性能,原因如下:在水溶液中显示正zeta电位值的TiO2与带负电的石墨烯/电气石复合物静电吸引而均匀紧密复合,有利于TiO2中光生电子和空穴的快速分离和传递,从而使得石墨烯/电气石/TiO2三元复合材料具有较高的光催化性能;而带正电的PDDA-石墨烯/电气石复合物和TiO2颗粒相互排斥而不宜复合,导致PDDA-石墨烯基复合材料的光催化活性降低.机理研究揭示,在三元复合材料光催化降解异丙醇的反应中起主要作用的是光生电子和空穴.基于以上研究结果,我们提出了三元复合材料光催化降解异丙醇的反应机理.     

Preparation of Ag deposited TiO2 (Ag/TiO2) composites and investigation on visible-light photocatalytic degradation activity in magnetic field

In this study, Ag deposited TiO₂ (Ag/TiO₂) composites were prepared by three different methods (Ultraviolet Irradiation Deposition (UID), Vitamin C Reduction (VCR) and Sodium Borohydride Reduction (SBR)) for the visible-light photocatalytic degradation of organic dyes in magnetic field. And then the prepared Ag deposited TiO₂ (Ag/TiO₂) composites were characterized physically by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The visible-light photocatalytic activities of these three kinds of Ag deposited TiO₂ (Ag/TiO₂) composites were examined and compared through the degradation of several organic dyes under visible-light irradiation in magnetic field. In addition, some influence factors such as visible-light irradiation time, organic dye concentration, revolution speed, magnetic field intensity and organic dye kind on the visible-light photocatalytic activity of Ag deposited TiO₂ (Ag/TiO₂) composite were reviewed. The research results showed that the presence of magnetic field significantly enhanced the visible-light photocatalytic activity of Ag deposited TiO₂ (Ag/TiO₂) composites and then contributed to the degradation of organic dyes.     

Improved photoelectric performance of DSSCs based on TiO2 nanorod array/Ni-doped TiO2 compact layer composites film

Journal of Solid State Electrochemistry - In spite of the TiO2 compact layer (TCL) being widely used, it still needs more study. This paper took Ni-doped TCLs as the research target, using an...     

介孔AgBr/TiO_2-SiO_2光催化剂的制备及其可见光催化活性

通过沉积法将光活性AgBr半导体负载到介孔TiO_2-SiO_2载体上合成了新型的AgBr/TiO_2-SiO_2复合光催化剂.采用X射线衍射仪、高分辨透射电镜、紫外-可见吸收光谱仪等分析了AgBr/TiO_2-SiO_2复合光催化剂的结构和光谱性质;并采用BET法测定了样品的比表面积和孔分布.结果表明,介孔TiO_2-SiO_2载体的比表面积为135.5m2/g,平均孔径约为3.8nm,AgBr的负载可以有效地将AgBr/TiO_2-SiO_2复合光催化剂的吸收光谱从紫外光区扩展到可见光区,且AgBr和TiO_2形成了异质结结构,强化了AgBr与介孔TiO_2-SiO_2载体的协同作用.以罗丹明B作为探针分子,评价了AgBr负载量对复合光催化剂可见光催化活性的影响.结果发现,当AgBr∶TiO_2=0.1,0.2,0.3和0.4(物质的量之比,下同)时,复合光催化剂的光催化反应速率常数分别为0.008 5、0.028 6、0.024 6和0.019 3min-1,活性先增加后减小,当AgBr∶TiO_2=0.2时,复合光催化剂表现出最高的光催化活性,并且在5次循环测试中均表现出较高的光催化活性.     

Bacterial cellulose/gelatin composites: in situ preparation and glutaraldehyde treatment

Bacterial cellulose (BC)/GEL composites were prepared in situ by adding gelatin into BC-producing culture medium. The addition of gelatin interfered with the formation of the BC pellicle structure and thus made the BC yield and growth rate quite different from that of pure BC. Scanning electron microscope images showed that the width of cellulose ribbons became narrower than that of pure BC and the gelatin filled in the pores of BC to form a dense structure. The addition level of gelatin significantly influences the yield of BC/GEL composites. An optimum value of 0.5 wt/v% gelatin was attained, with which the highest yield of 0.0541 g/100 mL was achieved. Under this condition, the weight percentage of gelatin in BC/GEL composite was 65 wt%. BC/GEL composites were treated with glutaraldehyde to crosslink BC fibrils and gelatin. The crosslinking degree, determined by the concentration of glutaraldehyde and crosslinking time, could affect the swelling behavior, thermal stability and mechanical properties of composites. With increasing of the crosslinking degree, the crystallinity index and swelling behavior of the composites decreased. The increase in the crosslinking degree also descreased the composite’s strain at break in elongation but increased the compressive and tensile strength. Covalent bonding between BC and gelatin provides good strength retention to the glutaraldehyde-treated composites with a high crosslinking degree. Considering the cytocompatibility and properties of composites, the most appropriate concentration of glutaraldehyde and crosslinking time were 1.0 wt/v% and 24 h, respectively.     

A photocatalytic comparison study between tin complex and carboxylic acid derivatives of porphyrin/TiO2 composites

Research on Chemical Intermediates - We synthesized a novel dihydroxotin(IV) porphyrin complex with full structural confirmation. The tin complex further converted to TiO2 composite...     

Facile preparation and characterization of anatase TiO2/nanocellulose composite for photocatalytic degradation of methyl orange

Anatase TiO₂/nanocellulose composite was prepared for the first time via a one-step method at a relatively low temperature by using cellulose nanofibers as carrier and tetrabutyl titanate as titanium precursor. The morphology, structure and element composition of the composite were characterized by SEM, EDS, TEM, XRD, XPS and UV–vis DRS. The specific surface area and thermal stability of the composite were investigated by N₂ adsorption–desorption and thermogravimetric analysis, respectively, and the band gaps of the prepared photocatalysts were calculated based on the UV–vis DRS results. In addition, the prepared composite was used for the photocatalytic degradation of methyl orange (aqueous solution, 40 mg L⁻¹). It was found that the composite had a good morphology and anatase crystal structure, and Ti-O-C bond was formed between TiO₂ and nanocellulose. The specific surface area of composite was increased and the thermal stability was decreased compared with the cellulose nanofiber. Moreover, the degradation rate of methyl orange was achieved as 99.72% within 30 min, and no obvious activity loss was observed after five cycles. This work might give some insights into the design of efficient photocatalysts for the treatment of organic dye wastewater.     

Low-temperature deposition and crystallization of RuO2/TiO2 on cotton fabric for efficient solar photocatalytic degradation of o-toluidine

A green low-temperature deposition and crystallization method was developed to uniformly coat RuO₂/TiO₂ nanocomposite onto cotton fabrics for efficient solar photocatalysis. The sequential growth of anatase TiO₂ and rutile RuO₂ on the surface of the cotton was confirmed by XRD, Raman and XPS characterizations. After the deposition of RuO₂, the optical properties of RuO₂/TiO₂/Cotton revealed better visible light absorption and higher charge mobility, and XPS spectra showed that the peaks of Ti 2p_3/2 and O 1 s shifted towards the lower binding energies due to the interfacial charge transfer at the robust RuO₂/TiO₂ mediated with Ti–O–Ru bonding. The photocatalytic performances of the RuO₂/TiO₂/Cotton were evaluated towards the photodegradation of o-toluidine (o-TD), an aromatic amine widely used in the chemical industry. Compared with TiO₂/Cotton, RuO₂/TiO₂/Cotton exhibited a remarkable improvement in the photocatalytic activity. The presence of RuO₂ on the surface of TiO₂/Cotton narrowed the band gap and improved the absorption of visible light. Moreover, the successful formation of a robust heterogeneous interface between TiO₂ and RuO₂ suppressed the charge carrier (e^–/h⁺) recombination effectively. With the RuO₂/TiO₂ coating chemically bound to the cotton fibers, RuO₂/TiO₂/Cotton delivered long-term stability in photocatalytic activity and high mechanical durability even after 20 washing times. Our facile and scalable synthesis strategy paved a universal route to efficient immobilization of visible-light-responsible TiO₂-based photocatalysts on the low-heat-resistant substrates for various applications.

Graphical abstract

     

原位制备氧化钛/氮掺杂石墨烯空心球光催化剂及其光催化CO2还原性能研究

利用光催化技术将二氧化碳转化为化学燃料是缓解温室效应以及能源危机的理想途径之一.因此,开发高效的光催化剂是当务之急.氧化钛由于具有优异的物理化学稳定性、成本低廉、无毒性以及环境友好等优点,近年来被广泛关注.此外,空心球结构光催化剂具有短的载流子扩散距离、良好的光散射性以及较大的比表面积等优点,从而成为光催化二氧化碳还原最有潜力的候选材料.但纯的氧化钛空心球由于较快的光生载流子复合速率从而导致低的光催化效率.因此,为了应对这一挑战,我们尝试在氧化钛空心球表面负载助催化剂用以促进光生载流子的分离,从而提高光催化二氧化碳还原转换效率.在各种助催化剂中,贵金属被证明是有效的.然而,高成本以及稀缺性限制了贵金属的广泛应用.因此,有必要设计成本低廉的助催化剂替代品.石墨烯以其优异的导电性、较大的功函数以及来源丰富而备受关注.当石墨烯与n型半导体光催化剂结合在一起时,能够显著促进光生电子从半导体光催化剂向石墨烯的定向迁移,从而有效地抑制光生电子与空穴的复合.当石墨烯中掺杂氮元素时,石墨烯骨架中的电子密度会进一步提高,同时,氮原子中的孤对电子更加有利于石墨烯骨架中的电子传输.此外,氮掺杂石墨烯中不同的氮位点(吡啶氮、吡咯氮和石墨氮)作为路易斯碱位点,能够用以二氧化碳分子的吸附以及活化.然而,迄今为止,最常用的制备半导体/氮掺杂石墨烯纳米复合光催化剂的方法是在氮掺杂石墨烯表面生长半导体光催化剂.所制备的光催化剂与氮掺杂石墨烯之间界面接触有限,不利于光生载流子的快速传递与分离.此外,助催化剂和光催化剂之间建立高质量的界面接触可以有效地抑制光生电子与空穴的复合.因此,有必要绕开传统制备方法的弊端,从而设计与光催化剂之间具有大的接触面积和紧密的界面接触以及具有丰富活性位点的高质量氮掺杂石墨烯助催化剂.本文提出了一种新的策略,以吡啶为氮掺杂石墨烯的前驱体,通过化学气相沉积方法在氧化钛空心球表面原位生长超薄氮掺杂石墨烯层(1～2层).此外,在高温状态下,吡啶分子脱氢生成具有优异扩散性质的脱氢吡啶自由基气相分子,随着反应的进行,氧化钛表面的每个纳米颗粒基元表面都能够与吡啶分子充分接触,从而保障两者之间大面积以及紧密的界面接触.光催化二氧化碳还原性能测试结果表明,优化后的氧化钛/氮掺杂石墨烯空心球纳米复合材料的二氧化碳光催化总转化率(一氧化碳、甲醇和甲烷的总产率)为18.11 μmol g-1 h-1,是空白氧化钛空心球的4.6倍和商业P25的10.7倍.高分辨透射电子显微镜、X射线光电子能谱以及拉曼光谱结果表明,成功构建了氧化钛与氮掺杂石墨烯之间紧密接触的界面.同时,氮掺杂石墨烯的引入能够显著增强复合光催化剂的表面光热效应以及氧化钛与氮掺杂石墨烯界面肖特基势垒的形成均有助于促进光催化二氧化碳还原反应的进行.因此,本文为石墨烯基光助催化剂的原位构建提供了一种行之有效的策略.