稀土离子掺杂改性TiO2光催化剂

TiO2较宽的禁带宽度和低的量子转换效率限制了其实际的应用,对TiO2进行改性以克服上述两方面问题一直是光催化领域研究的重点。稀土元素因其独有的电子结构和光学性质,在离子掺杂改性TiO2研究中受到重点关注。主要介绍了稀土离子掺杂改性TiO2所形成杂质能级的位置对改善其光催化性能的作用机理;综述了稀土离子掺杂对TiO2的晶型、晶粒尺寸和光谱吸收的影响;最后提出了目前研究存在的问题及发展趋势。     

镍掺杂TiO2光催化剂的制备及光催化性能

采用溶胶-凝胶法制备镍掺杂纳米TiO2光催化剂。通过XRD、XPS、FT-IR、UV-Vis、PL等对Ni-TiO2样品进行表征和分析,并以亚甲基蓝(MB)作为目标降解物,考察经不同热处理温度及不同掺镍量Ni-TiO2样品对MB的降解效果。结果表明所制备的Ni-TiO2样品的晶型为锐钛矿相与金红石相的混晶相,镍掺杂抑制了晶粒的生长和晶型的转变,样品的吸收阈值波长向可见光红移约55nm,提高了TiO2的光催化活性。在普通日光灯下,经500℃热处理、掺镍量与TiO2摩尔比为1∶100条件下制备的催化剂其光催化活性明显高于Degussa P25。     

离子掺杂改性TiO2光催化剂的理论研究进展

光催化技术是一种治理环境污染的新技术,但由于存在2个瓶颈问题(光催化活性需要紫外光激发及量子转换效率低)而制约了其推广应用。围绕上述问题,国内外开展了大量的改性研究并取得了一定的成果,尤其是近年来开始重视该方面的理论研究,这对推动光催化技术的发展起到了重要作用。介绍了本课题组及文献报道的对离子掺杂锐钛矿相TiO2光催化材料理论研究方面取得的主要结果,总结了不同离子掺杂及共掺杂对TiO2晶体结构、电子结构、光学性质和光催化性能的影响规律,提出了如何选择合适的掺杂离子以便有效地提高TiO2光催化性能的方法。     

不同离子掺杂条件下TiO2的光催化机理及应用研究进展

作为光催化技术的核心材料TiO₂,由于其独特的结构和性能,使其在污水处理、能源及医疗美容等方面具有巨大的潜力。但其存在禁带宽度大且激发波长短、光生电子容易复合等问题已成为其应用的重要瓶颈问题之一。介绍TiO₂材料的光催化原理和影响因素,重点阐明了掺杂改性TiO₂光催化机理及其应用领域,提出了TiO₂光催化剂改性过程中存在的不足之处,并对其未来的研究方向进行了展望。     

贵金属改性TiO2光催化剂的机理及研究进展

利用贵金属改性TiO2光催化剂是提高TiO2光催化活性的主要方法之一,在离子掺杂改性TiO2研究中受到重点关注。综述了贵金属改性TiO2光催化剂的机理,总结了贵金属改性TiO2光催化剂的主要制备方法,分析了目前贵金属改性TiO2光催化剂研究中存在的问题,指出通过某些贵金属掺杂TiO2光催化剂能克服贵金属表面沉积改性方法的不足,并能有效改善TiO2光催化剂的光催化性能。     

镧掺杂TiO2/有机改性膨润土复合光催化材料的制备及性能

本文采用十六烷基三甲基溴化铵对钠基膨润土进行改性,并以有机改性膨润土作为载体,采用超声辅助溶胶-凝胶法制备了镧掺杂TiO2/有机改性膨润土复合光催化材料,采用X射线衍射(XRD)、傅里叶变换红外(FT-IR)光谱和紫外-可见漫反射吸收光谱(DRS)等测试技术对其进行了表征分析,以TNT溶液作为目标物,考察了复合材料的吸附性能和光催化性能。结果表明:膨润土的有机改性抑制了TiO2的晶粒生长,增强了复合材料的吸光性能,提高了复合材料的吸附和光催化性能。     

稀土元素与N共掺杂TiO2光催化剂的研究进展

TiO2作为一种重要的光催化剂,对其进行掺杂改性可有效扩展其光谱响应范围,提高其光催化活性。介绍了稀土元素与N对TiO2进行共掺杂改性的机理及研究现状,分析了共掺杂对TiO2晶体结构、电子结构以及光学性能、氧化还原性能的影响,总结了稀土元素与N共掺杂改性TiO2存在的问题以及今后的研究前景。     

B掺杂TiO2光催化剂的制备和光催化性能

采用溶胶-凝胶法合成了B掺杂的TiO₂光催化剂,并用XRD、SEM、XPS、FT-IR、BET等手段进行了表征。结果表明,掺杂B可抑制TiO₂晶体的长大,对TiO₂表面形貌没有显著的影响,B-TiO₂催化剂的比表面积随着B离子掺杂量的提高而增大;B离子主要进入晶格间隙并与TiO₂晶体形成固溶体,以B-O-Ti结构存在。B掺杂量（质量分数）为3%时,制备出的TiO₂光催化剂对甲基橙的降解效果最好。N₂吸附-脱附结果表明,3%B-TiO₂的BET比面积为127.84 m²/g、平均孔径为10.53 nm。     

氮掺杂氧缺陷TiO2光催化剂的制备和性能

采用NH3-H2气氛两步热处理法制备氮掺杂氧缺陷TiO2,用X射线粉末衍射、N2吸附BET法、X射线光电子能谱、元素分析、电子自旋共振谱、紫外可见漫反射光谱和荧光光谱等技术对样品的晶相结构、表面化学状态、氮含量、氧缺陷位种类及含量、光吸收性能和光生载流子的分离效率等性质进行了表征,研究了H2气氛中不同热处理时间对催化剂性能的影响和催化剂样品在可见光(λ>400 nm)条件下的光催化氧化能力。结果表明,掺氮TiO2催化剂经H2热处理1 h后具有较好的可见光催化活性,对苯的转化率和矿化率分别为66.8%和47.5%,其降解效率高于单掺杂催化剂活性的总和,双掺杂光催化剂活性的提高与氮杂质氧缺陷双光活性中心的协同增强作用有关。     

CdS、Ag+掺杂改性纳米TiO2光催化降解有机物研究

在理论分析的基础上对纳米TiO₂分别进行掺CdS和掺银改性实验研究。采用XRD和粒度分析技术对改性后的样品进行表征,并以掺杂CdS、Ag⁺纳米TiO₂进行光催化降解甲基橙模拟实验。结果表明,掺杂CdS、Ag⁺纳米TiO₂在可见光范围内降解有机物的效率有较大提高。     

Yb-TiO2光催化剂的制备及性能研究

采用溶胶-凝胶法制备了稀土Yb掺杂纳米TiO2光催化剂(Yb-TiO2),采用XRD、UV-Vis、FT-IR等方法对其进行表征和分析,并以亚甲基蓝(MB)作为目标降解物,考察了热处理温度以及Yb掺杂量对样品性能的影响。实验结果表明,Yb掺杂样品均为金红石相和锐钛矿相的混晶相,Yb的掺入拓展了TiO2对可见光的吸收范围,有效地抑制了光生电子-空穴对的复合,提高了TiO2的光催化活性。当pH值=2.5、n(Yb)∶n(Ti)=0.005、热处理温度为650℃时,制备的样品其光催化活性明显优于Degussa P25。     

Large-sized nano-TiO2/SiO2 mesoporous nanofilm-constructed macroporous photocatalysts with excellent photocatalytic performance

Novel large-sized mesoporous nanofilm-constructed macroporous SiO₂ (LMNCMS) with two sets of well-defined 3D continuous pass-through macropores (pore size of 0.5–1.0 μm, wall thickness of 40–50 nm) was prepared through a dual-templating approach, and used as an advanced support for TiO₂ nanocrystalline photocatalyst. The structural and optical properties of the as-prepared materials were investigated by various characterization techniques in order to explore the connections between catalysts’ features and catalytic performance. The photocatalytic activities were evaluated by degradations of methylene blue (MB) and phenol under the simulated sunlight irradiation. To gain insight into the impact of preparation and operation conditions on photocatalytic degradation processes, experiments were conducted at wide ranges of the TiO₂ loading content, calcination temperature, solution pH, and photocatalyst dosage. Nano-TiO₂/LMNCMS exhibited high photocatalytic activity and stability. Rapid matter transport, good accessibility of pollutants to TiO₂ and high light harvesting could mainly account for the superior photocatalytic performance. The trapping experiments were performed to identify the main reactive species in the catalytic reactions.     

网状结构Bi2O3光催化剂的合成及其光催化性能

以Bi(NO3)3·5H2O为原料,天然棉花为模板结合热处理工艺,成功合成了具有网状结构的三斜晶相Bi2O3光催化材料,利用XRD、SEM、TG-DTA和UV-Vis漫反射等技术对样品的晶型结构、形貌及吸光性能等进行了表征。以亚甲基蓝染料分子模拟环境污染物,考察了样品的光催化性能。结果表明,棉花纤维在网状Bi2O3的制备中起到了充分的诱导作用,这种网状结构是由一些直径不一的Bi2O3扁平状网线交错排列、稀疏盘结而形成。TGA分析结果表明,适当的热处理在去除棉花模板的同时可以实现Bi 3+→Bi2O3的转化。在可见光照射下,网状Bi2O3的光催化活性及重复使用性能均优于粉体Bi2O3,反应100min后,对MB的脱色率可达到93%左右,并且重复使用4次后仍可使MB的脱色率保持在85%以上。此外,对网状Bi2O3的形成机理进行了探讨。     

Effect of TiO2/adsorbent hybrid photocatalysts for toluene decomposition in gas phase

12 hybrid photocatalysts consisting of titania (TiO₂) and an adsorbent such as mordenite were investigated for the photocatalytic decomposition of toluene, a major indoor contaminant in indoor air. The highest decomposition rate was obtained with the use of mordenite and silicon dioxide (SiO₂) as additives to TiO₂. The photocatalytic activities of hybrid photocatalysts in decomposing toluene are 1.33 times as high as pure P25 at the net weight loading of 0.49 mg/cm² under the test condition. Scanning electron microscopy (SEM) images confirmed that the hybrid photocatalyst films were very porously distributed; TiO₂ was adsorbed on the surface of mordenite and SiO₂, increasing the reaction area of TiO₂. The unimolecular Langmuir–Hishelwood model and mass-transfer-based (MTB) method were used to evaluate the reaction coefficients and adsorption equilibrium coefficients of hybrid photocatalysts. It is evidenced that the reaction areas of two hybrid photocatalysts were 1.52 and 1.64 times larger than that of P25, respectively, which is the major reason to make the high removal efficiency of toluene.     

Preparation and visible photocatalytic dye degradation of Mn-TiO2/sepiolite photocatalysts

The performance of Mn-TiO₂/sepiolite photocatalysts prepared by the sol-gel method and calcinated at different temperatures was studied in the photocatalytic degradation of direct fast emerald green dye under visible light irradiation, and a series of analytical techniques such as XRD, SEM, FTIR, TG-DSC, XPS, UV-vis-DRS and Raman spectroscopy were used to characterize the morphology, structure and optical properties of the photocatalysts. It is found that the anatase TiO₂ was formed in all photocatalysts. Mn⁴⁺ might incorporate into the lattice structure of TiO₂ and partially replace Ti⁴⁺, thus causing the defects in the crystal structure and the broadening of the spectral response range of TiO₂. At the same time, TiO₂ particles were dispersed on the surface of the sepiolite, which immobilized TiO₂ particles with sepiolite via the bond of Ti−O−Si. Mn-TiO₂/sepiolite calcined at 400 °C exhibits the highest photocatalytic activity and the degradation rate of direct fast emerald green is up to 98.13%. Meanwhile, it also shows good stability and universality.     

Photophysical and photocatalytic properties of novel Y2GaSbO7 and Y2YbSbO7 photocatalysts under visible light irradiation

Y₂GaSbO₇ and Y₂YbSbO₇ were synthesized by solid state reaction method for the first time. The crystallinity, composition, bandgap, morphology, and grain size of Y₂GaSbO₇ and Y₂YbSbO₇ were characterized by a series of analytical techniques. The lattice parameter a for Y₂GaSbO₇ was found to be 10.17981(1) ?, and the lattice parameters for Y₂YbSbO₇ were found to be a = 10.49741(9) ?, b = 7.45088(3) ?, c = 7.47148(7) ?, respectively. The values of band gap for Y₂GaSbO₇ and Y₂YbSbO₇ were calculated to be 2.245 and 2.521 eV, respectively. The photocatalytic degradation of rhodamine B (RhB) with Y₂GaSbO₇ or Y₂YbSbO₇ as photocatalyst was investigated under visible light irradiation. The results showed that Y₂GaSbO₇ and Y₂YbSbO₇ owned higher photocatalytic activity compared with Bi₂InTaO₇. Moreover, Y₂GaSbO₇ showed higher photocatalytic activity compared with Y₂YbSbO₇ for the photocatalytic degradation of RhB. The photocatalytic degradation of RhB followed the first-order reaction kinetics. The first-order rate constant, k, was 0.01817, 0.01341, and 0.00329 min⁻¹ for Y₂GaSbO₇, Y₂YbSbO₇, and Bi₂InTaO₇, respectively. Complete removal of RhB was realized after visible light irradiation for 220 or 240 min with Y₂GaSbO₇ or Y₂YbSbO₇ as photocatalyst. The reduction of the total organic carbon and the evolution of CO₂ were also realized and these results indicated the continuous mineralization of RhB during the photocatalytic process with Y₂GaSbO₇ or Y₂YbSbO₇ as photocatalyst. The possible photocatalytic degradation pathway of RhB was revealed under visible light irradiation. Methylene blue and neutral red could be degraded efficiently with Y₂GaSbO₇ or Y₂YbSbO₇ as photocatalyst under visible light irradiation.     

Selective-syntheses, characterizations and photocatalytic activities of nanocrystalline ZnTa2O6 photocatalysts

Nanocrystalline ZnTa₂O₆ photocatalysts with different crystal structures were prepared via a simple and facile sol-gel method in a temperature range of 650-950 °C. The absorption edges and particle sizes of the samples were located at about 285 nm (corresponding a band gap of 4.35 eV) and ranged from 25 to 150 nm, respectively. The photocatalytic activities of the samples were tested by the degradation of methyl orange under UV light irradiation. The results indicated that the crystal structure of ZnTa₂O₆ was a main factor for the different photocatalytic activities of the ZnTa₂O₆ samples. Moreover, the effects of crystallinities and surface areas of the obtained samples on the catalytic activities were also discussed.     

Photocatalytic degradation of pendimethalin over Cu2O/SnO2/graphene and SnO2/graphene nanocomposite photocatalysts under visible light irradiation

The Cu₂O/SnO₂/graphene (CSG) and SnO₂/graphene (SG) nanocomposite photocatalysts were prepared by simple sol-gel growth method, and characterized by Fourier transform infrared spectra (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) measurements, respectively. The photocatalytic efficiency of catalysts were evaluated by degradation of pendimethalin under visible light irradiation (λ > 420 nm), which conformed that CSG and SG exhibited better photocatalytic activity than SnO₂ or graphene alone. An effort has been made to correlate the photoelectro-chemical behavior of these samples to the rate of photocatalytic degradation of pendimethalin.     

Solar photocatalytic degradation of 2-sec-butyl-4,6-dinitrophenol (DNBP) using TiO2/SiO2 aerogel composite photocatalysts

Silica aerogels and TiO₂/silica aerogel composite photocatalysts were synthesized by sol–gel technique at ambient pressure using orthosilioate and tetra-n-butyl titanate as precursors, respectively. The prepared composite photocatalysts were characterized by XRD, TEM, BET surface area, FT-IR and UV–vis absorption spectra. The results showed that the TiO₂/silica aerogel composite photocatalysts possess high surface area. The addition of silica aerogels inhibited the grain growth and phase transformation of anatase to rutile during calcination. The TiO₂/silica aerogel composite sample calcined at 500 °C with an optimal silica aerogel content of 7 wt.% afforded the highest photocatalytic activity. The photocatalytic degradation of 2-sec-butyl-4,6-dinitrophenol (DNBP) was investigated by using this novel TiO₂/silica aerogel composite photocatalyst under solar light irradiation. The effects of irradiation time, pH, catalyst concentration, temperature and initial DNBP concentration were examined as operational parameters. The optimal operational parameters were found as follows: pH as solution pH 4.82, 8 g L⁻¹ catalyst concentration, 20 °C, and 240 min irradiation time. The kinetics of DNBP degradation by TiO₂/silica aerogel composite fit well a pseudo-first-order kinetic model. The repeatability of photocatalytic activity was also tested. This study showed the feasible and potential use of TiO₂/silica aerogel composite photocatalysts in degradation of toxic organic contaminants.     

Controlled synthesis of Pt-loaded yolk–shell TiO2@SiO2 nanoreactors as effective photocatalysts for hydrogen generation

Yolk–shell and hollow structures are powerful platforms for controlled release, confined nanocatalysis, and optical and electronic applications. This contribution describes a fabrication strategy for a yolk–shell nanoreactor (NR) using a post decoration approach. The widely studied yolk–shell structure of silica-coated TiO₂ (TiO₂@SiO₂) was used as a model. At first, anatase TiO₂ spheres were prepared, and subsequently were given a continuous coating of carbonaceous and silica layers. Finally, the carbonaceous layer was removed to produce a yolk–shell structure TiO₂@SiO₂. By using an in-situ photodeposition method, Pt-encased spheres (Pt-TiO₂@SiO₂) were synthesized with Pt nanoparticles grown on the surface of the TiO₂ core, which contained void spaces suitable for use as NRs. The NR showed enhanced hydrogen production with a rate of 24.56 mmol·g⁻¹·h⁻¹ in the presence of a sacrificial agent under simulated sunlight. This strategy holds the potential to be extended for the synthesis of other yolk–shell photocatalytic NRs with different metal oxides.