磷掺杂TiO2薄膜的制备与表征及其可见光照射下光催化降解邻苯二甲酸丁苄酯性能（英文）

P‐doped TiO2 (PTIO) thin‐films with different P contents were prepared using a sol‐gel method. The thin‐film samples were characterized using various techniques. The photocatalytic activity was evaluated by decomposing butyl benzyl phthalate under visible‐light irradiation. The results showed that the transformation of anatase to the rutile phase was inhibited and grain growth of TiO2 was prevented by P doping. The results confirm that the doped P atoms existed in two chemical forms, and those incorporated in the TiO2 lattice may play a positive role in photocatalysis. The high photocatalytic activities of the PTIO thin‐films may be the result of extrinsic absorption through the creation of oxygen vacancies, rather than excitation of the intrinsic absorption band of bulk TiO2 . The PTIO can be recycled with little depression of the photocatalytic activity. After six cycles, the photocatalytic activity of the PTIO film was still higher than 98%.     

Catalytic Role of TiO2 Terminal Oxygen Atoms in Liquid‐Phase Photocatalytic Reactions: Oxidation of Aromatic Compounds in Anhydrous Acetonitrile

On the basis of experiments carried out with controlled amounts of residual oxygen and water, or by using oxygen‐isotope‐labeled Ti¹⁸O₂ as the photocatalyst, we demonstrate that ¹⁸O_s atoms behave as real catalytic species in the photo‐oxidation of acetonitrile‐dissolved aromatic compounds such as benzene, phenol, and benzaldehyde with TiO₂. The experimental evidence allows a terminal‐oxygen indirect electron‐transfer (TOIET) mechanism to be proposed, which is a new pathway that involves the trapping of free photogenerated valence‐band holes at O_s species and their incorporation into the reaction products, with simultaneous generation of oxygen vacancies at the TiO₂ surface and their subsequent healing with oxygen atoms from either O₂ or H₂O molecules that are dissolved in the liquid phase. According to the TOIET mechanism, the TiO₂ surface is not considered to remain stable, but is continuously changing in the course of the photocatalytic reaction, challenging earlier interpretations of TiO₂ photocatalytic phenomena.     

熔融盐法制备富氧空位TiO2纳米片及其光催化性能

氧空位缺陷对半导体材料性能的积极作用引起人们越来越多的关注。本文中,以TiCl4在三氟乙酸中的水解产物为前驱体,通过一步熔融盐法成功合成了具有富氧空位的蓝色TiO2纳米片。由于熔融盐低的氧分压,使前驱体在煅烧过程中消耗了TiO2中的晶格氧从而产生大量的氧空位和Ti3+。紫外-可见漫反射光谱测试表明,蓝色TiO2纳米片的带隙宽度减小至2.69eV,光吸收范围从紫外光区拓宽到可见光区。所制备的蓝色TiO2纳米片表现出优异的光催化活性,在全光谱照射下,对若丹明B的光降解速率是纯TiO2的47.3倍。同时,形成的晶格氟掺杂能有效地稳定氧空位,极大地提高了光生载流子的分离效率。本工作为在半导体氧化物材料内构建氧空位提供了新的思路。     

Band Structure Engineering of Single Pt Atoms on Fe−TiO2 for Enhanced Photocatalytic Performance

Single atomic site catalysts display the maximal atom-utilization efficiency, unique structural properties, and remarkable enhancements on catalytic activity. Herein, single Pt atoms loaded Fe−TiO₂ catalysts were prepared. Fe³⁺ doping leads to the formation of oxygen vacancies and improve the interaction between TiO₂ and Pt. Single Pt atoms are thus anchored and effectively modify the local energy band structure of TiO₂. The optimized local band structures improve the intrinsic photoexcitation of Pt/Fe−TiO₂, promote the separation of photogenerated carriers, and extend the lifetime of photogenerated carriers. Meanwhile, the electrons transfer from the excited dyes to the conduction band edge of Pt/Fe−TiO₂ is also facilitated due to the shift-down of the conduction band edge. Therefore, with the increase of the Pt content (till up to 0.6 wt%), the photocatalytic performance of Pt/ Fe−TiO₂ with the confined single Pt atoms is significantly boosted in either the intrinsic or the sensitized photocatalytic process.     

Fluorine-doped TiO2 powders prepared by spray pyrolysis and their improved photocatalytic activity for decomposition of gas-phase acetaldehyde

F-doped TiO₂ (FTO) powders were synthesized by spray pyrolysis (SP) from an aqueous solution of H₂TiF₆. The resulting FTO powders possessed spherical particles with a rough surface morphology and a strong surface acidity. The fluorine concentrations in the FTO powders calculated from XPS spectra significantly depended on SP temperature and ranged from 2.76 to 9.40 at.%. The FTO powder prepared at SP temperature of 1173 K demonstrated the highest photocatalytic activity for the decomposition of gas-phase acetaldehyde under both ultraviolet (UV) and visible light (vis) irradiations, and it was higher than that of commercial P 25. This high photocatalytic activity was ascribed to several beneficial effects produced by F-doping: enhancement of surface acidity, creation of oxygen vacancies, and increase of active sites. It was interesting to point out that the vis photocatalytic activity of FTO powders was achieved by the creation of surface oxygen vacancies rather than the improvement of optical absorption property of bulk TiO₂ in vis region.     

The Influence of Defects on Mo‐Doped TiO2 by First‐Principles Studies

TiO₂ doped with transition metals shows improved photocatalytic efficiency. Herein the electronic and optical properties of Mo‐doped TiO₂ with defects are investigated by DFT calculations. For both rutile and anatase phases of TiO₂, the bandgap decreases continuously with increasing Mo doping level. The 4d electrons of Mo introduce localized states into the forbidden band of TiO₂, and this shifts the absorption edge into the visible‐light region and enhances the photocatalytic activity. Since defects are universally distributed in TiO₂ or doped TiO₂, the effect of oxygen deficiency due to oxygen vacancies or interstitial Mo atoms is systemically studied. Oxygen vacancies associated with the Mo dopant atoms or interstitial Mo will reduce the spin polarization and magnetic moment of Mo‐doped TiO₂. Moreover, oxygen deficiency has a negative impact on the improved photocatalytic activity of Mo‐doped TiO₂. The current results indicate that substitutional Mo, interstitial Mo, and oxygen vacancy have different impacts on the electronic/optical properties of TiO₂ and are suited to different applications.     

The electronic structure of intrinsic defects at TiO2 (110) surfaces: An ab initio molecular orbital study

We report on an isolated cluster approach to determine local electronic structures of TiO₂ surfaces before and after formation of intrinsic defects, i.e., oxygen vacancies, at different crystallographic sites. In particular, isolated oxygen vacancies at bridging sites, isolated oxygen vacancies at in-plane sites and aggregated oxygen vacancies at bridging sites have been treated which lead to changes in the coordination of the adjacent Ti atoms. We find that electronic band gap states are only formed in the presence of fourfold coordinated Ti surface atoms. © 1996 John Wiley & Sons, Inc.     

金红石相TiO2纳米棒的氢化处理及其光催化活性

以钛酸四丁酯为钛源,通过盐酸调制的水热法制备出了具有棒状结构的金红石相纳米TiO₂,并进一步进行高温氢化处理. 采用X射线衍射（XRD）,透射电镜（TEM）,紫外-可见-近红外漫反射（UV-Vis-NIR DRS）,电子顺磁共振（EPR）和表面光伏（SPS）等测试手段对样品进行表征,以气相乙醛和液相苯酚为目标污染物考察催化剂的光催化活性. 结果表明：随着高温氢化处理时间的延长,TiO₂样品的可见光吸收逐渐增强,其颜色逐渐由白色转变成灰色,这主要与引入的Ti³⁺/氧空位缺陷有关. 表面光电压谱和羟基自由基测试表明,适当时间的氢化处理有利于光生电荷的分离. 在光催化氧化降解气相乙醛和液相苯酚过程中,经适当时间氢化处理的样品表现出高的可见光催化活性. 并且可见光催化活性的规律与紫外光下的是一致的. 这是因为氢化处理后在导带底下方引入了缺陷能级,拓展了可见光响应. 过度的氢化处理会在TiO₂导带下方引入较低的缺陷能级,使光生电荷的复合加剧,导致光催化活性降低.     

Probing the Electronic Structure and Photoactivation Process of Nitrogen‐Doped TiO2 Using DRS,PL, and EPR

The electronic structure and photoactivation process in N‐doped TiO₂ is investigated. Diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and electron paramagnetic resonance (EPR) are employed to monitor the change of optical absorption ability and the formation of N species and defects in the heat‐ and photoinduced N‐doped TiO₂ catalyst. Under thermal treatment below 573 K in vacuum, no nitrogen dopant is removed from the doped samples but oxygen vacancies and Ti³⁺ states are formed to enhance the optical absorption in the visible‐light region, especially at wavelengths above 500 nm with increasing temperature. In the photoactivation processes of N‐doped TiO₂, the DRS absorption and PL emission in the visible spectral region of 450–700 nm increase with prolonged irradiation time. The EPR results reveal that paramagnetic nitrogen species (N_s^.), oxygen vacancies with one electron (V_o^.), and Ti³⁺ ions are produced with light irradiation and the intensity of N_s^. species is dependent on the excitation light wavelength and power. The combined characterization results confirm that the energy level of doped N species is localized above the valence band of TiO₂ corresponding to the main absorption band at 410 nm of N‐doped TiO₂, but oxygen vacancies and Ti³⁺ states as defects contribute to the visible‐light absorption above 500 nm in the overall absorption of the doped samples. Thus, a detailed picture of the electronic structure of N‐doped TiO₂ is proposed and discussed. On the other hand, the transfer of charge carriers between nitrogen species and defects is reversible on the catalyst surface. The presence of oxygen‐vacancy‐related defects leads to quenching of paramagnetic N_s^. species but they stabilize the active nitrogen species N_s^?.     

Effect of Doping on Rutile TiO2 Surface Stability and Crystal Shapes

Transition-metal-(TM-)doped TiO₂ has been considered as promising electrode material for the oxygen evolution reaction (OER). OER activity is expected to depend on the coordination of the surface atoms. In this study, we theoretically investigate the stability of low-index surfaces of TM-doped rutile, (110), (100), (101) and (001), with 50 % of the Ti atoms substituted by Sc, Y, V, Nb or Ta. For Sc and Y, we also consider models with O vacancies providing the most stable oxidation state of Sc and Y. Surface energies are calculated with DFT(+U). Based on the Gibbs-Wulff theorem, the shape of the single crystals is predicted. It is observed that p-doping leads to spontaneous oxygen loss and O vacancies cause surface reconstruction. The Wulff shapes of n-doped TiO₂ have smaller contributions of the (110) facet and, for Nb and Ta, larger contributions of other facets. Given the higher coordinative unsaturation of the TM atoms in the latter, a higher catalytic activity is expected.     

Controllable Synthesis of Inverse Opal TiO2‐x Photonic Crystals and Their Photoelectric Properties

In this study, inverse opal TiO_2‐x photonic crystals (IO‐TiO_2‐x) have been successfully synthesized by a two‐step calcination. The whole synthesis is safe and feasible. Additionly, the reduction degree and the structure of IO‐TiO_2‐x can be precisely controlled. A series of IO‐TiO_2‐x samples with different reduction degree were prepared and characterized. The TEM images show that the obtained samples possess a 3D‐ordered macroporous inverse opal structure. The reduced Ti atoms/oxygen vacancies were confirmed by Raman and XPS spectroscopy. All IO‐TiO_2‐x samples showed better photoelectric properties than those of common TiO₂ which indicates their great potential to be applied to photoelectric fields. The improvement of photoelectric properties is attributed to the efficient electron‐hole separation efficiency induced by moderately reduced Ti atoms/oxygen vacancies. Meanwhile, the 3D‐ordered macroporous inverse opal structure and the band gap are regulated to “capture” more solar energy. This new approach is proven to be a meaningful method to synthesize high‐performance TiO₂ materials.     

Effect of the Structure of Small Anatase Nanoparticles on the Localization of Photogenerated Charge Carriers

The structure of nanoparticles and the spatial arrangement of photogenerated thermalized charge carriers are studied for a series of isomers of small anatase nanoparticles (TiO₂)₂₉(H₂O)₄, (TiO₂)₇₀(H₂O)₄, and (TiO₂)₇₀ with faces (001) and (101) on the surface. It is shown that the location of surface hydroxyl groups and their replacement by surface oxygen atoms affect the nature and degree of deformation of the nanoparticle structure. The location of the boundary orbitals depends both on the size of the nanoparticles and on the location of the hydroxyl groups, as well as on the degree of dehydroxylation, which leads to the replacement of the hydroxyl groups by the surface oxygen atoms. In the case of a certain arrangement of hydroxyl groups or surface oxygen atoms, uncharged small stoichiometric anatase nanoparticles begin to absorb light in the visible region of the spectrum (the band gap width E_g decreasing to 2.25 eV). This is associated with the energy levels at the edge of the band gap near the valence band and the conduction band.     

Engineering the Atomic Interface with Single Platinum Atoms for Enhanced Photocatalytic Hydrogen Production

It is highly desirable but challenging to optimize the structure of photocatalysts at the atomic scale to facilitate the separation of electron–hole pairs for enhanced performance. Now, a highly efficient photocatalyst is formed by assembling single Pt atoms on a defective TiO₂ support (Pt₁/def‐TiO₂). Apart from being proton reduction sites, single Pt atoms promote the neighboring TiO₂ units to generate surface oxygen vacancies and form a Pt‐O‐Ti³⁺ atomic interface. Experimental results and density functional theory calculations demonstrate that the Pt‐O‐Ti³⁺ atomic interface effectively facilitates photogenerated electrons to transfer from Ti³⁺ defective sites to single Pt atoms, thereby enhancing the separation of electron–hole pairs. This unique structure makes Pt₁/def‐TiO₂ exhibit a record‐level photocatalytic hydrogen production performance with an unexpectedly high turnover frequency of 51423 h^?1, exceeding the Pt nanoparticle supported TiO₂ catalyst by a factor of 591.     

Preparation of Er3+:Y3Al5O12/TiO2 composite film and influence of layer number and layer sequence on the visible-light photocatalytic activity

In this work, the Er³⁺:Y₃Al₅O₁₂ as up-conversion luminescence agent was mixed with TiO₂ and the corresponding Er³⁺:Y₃Al₅O₁₂/TiO₂ composite films were prepared on the one-sided surface of treated sheet glass through sol-gel dip-coating method. The prepared Er³⁺:Y₃Al₅O₁₂/TiO₂ composite films were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Their photocatalytic activities were examined through the degradation of some organic dyes under visible-light irradiation. The degradation process of organic dyes was monitored by UV-Vis spectrophotometer. Furthermore, some main influence factors on the visible-light photocatalytic activity of Er³⁺:Y₃Al₅O₁₂/TiO₂ composite film such as heat-treatment temperature and heat-treatment time were studied. The results indicate that three layer Er³⁺:Y₃Al₅O₁₂/TiO₂ composite films with one Er³⁺:Y₃Al₅O₁₂/TiO₂ composite film (as first layer close to sheet glass) and two pure TiO₂ film (as second and third layers) display a higher visible-light photocatalytic activity during photocatalytic degradation of Azo Fuchsine. In addition, the results showed that the visible-light photocatalytic activity of Er³⁺:Y₃Al₅O₁₂/TiO₂ composite film related to the layer number and layer sequence on the sheet glass. Perhaps, the research results may offer some meaningful references for developing solar energy continuous flow wastewater treatment reactor.     

The preparation and characterization of La doped TiO2 nanoparticles and their photocatalytic activity

In this paper, pure and La doped TiO₂ nanoparticles with different La content were prepared by a sol-gel process using Ti (OC₄H₉)₄ as raw material, and also were characterized by XRD, TG-DTA, TEM, XPS, DRS and Photoluminescence (PL) spectra. We mainly investigated the effects of calcining temperature and La content on the properties and the photocatalytic activity for degrading phenol of as-prepared TiO₂ samples, and also discussed the relationships between PL spectra and photocatalytic activity as well as the mechanisms of La doping on TiO₂ phase transformation. The results showed that La³⁺ did not enter into the crystal lattices of TiO₂ and was uniformly dispersed onto TiO₂ as the form of La₂O₃ particles with small size, which possibly made La dopant have a great inhibition on TiO₂ phase transformation; La dopant did not give rise to a new PL signal, but it could improve the intensity of PL spectra with a appropriate La content, which was possibly attributed to the increase in the content of surface oxygen vacancies and defects after doping La; La doped TiO₂ nanoparticles calcined at 600°C exhibited higher photocatalytic activity, indicating that 600°C was an appropriate calcination temperature. The order of photocatalytic activity of La doped TiO₂ samples with different La content was as following: 1>1.5>3>0.5>5>0 mol%, which was the same as the order of their PL intensity, namely, the stronger the PL intensity, the higher the photocatalytic activity, demonstrating that there were certain relationships between PL spectra and photocatalytic activity. This could be explained by the points that PL spectra mainly resulted from surface oxygen vacancies and defects during the process of PL, while surface oxygen vacancies and defects could be favorable in capturing the photoinduced electrons during the process of photocatalytic reactions.     

Induced zinc desorption from zinc oxide during exposure to a reducing agent

CH₃CH₂OD (deuterated ethanol) pulses (5 × 10^–4 ML, 20 ms) are offered to polycrystalline ZnO under ultra high vacuum conditions. The reaction products are monitored with a rate of 1000 spectra per second by a time of flight mass spectrometer. D₂O and CO₂, both including lattice oxygen, are observed in desorption. The creation of surface oxygen vacancies destabilizes zinc atoms nearby which appear also in desorption. The rate constant k_a (inverse relaxation time) increases below 900 K. Above this temperature k_a decreases. The decrease may be due to bulk oxygen diffusing to the surface and refilling the surface oxygen vacancies.     

组合型Pt/TiO_2催化剂用于低温催化甲苯完全氧化

将均匀分布的纳米Pt粒子直接吸附到TiO2载体上,即制得了组合型Pt/TiO2催化剂(Pt/TiO2-AS).与浸渍法制备的Pt/TiO2催化剂(Pt/TiO2-WI)比较,Pt/TiO2-AS催化剂在催化甲苯完全氧化反应中表现出了很好的催化性能,甲苯转化率为100%时的反应温度低至150°C,而且即使在较高甲苯浓度和较高气体空速下,该催化剂也能保持较好的催化性能.通过X射线衍射(XRD)、N2吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、氢气程序升温还原(H2-TPR)及傅里叶变换红外(FTIR)光谱等对两种Pt/TiO2催化剂的结构和表面性能进行了表征.结果表明组合型Pt/TiO2-AS催化剂粒径小(2.5 nm),活性组分主要以Pt0形式存在且分布在载体表面,而且载体表面Ti―O键活化使催化剂具有较强的催化氧化能力.另外,活性中心的价态变化(Pt0→Ptδ+)是导致Pt/TiO2-AS催化剂失活的主要原因.     

掺氮TiO2可见光降解有机污染物的比较研究

用溶胶-凝胶法制备了不同掺杂量的N/TiO₂复合纳米粉末, 采用X射线衍射(XRD)、扫描透镜(TEM)、紫外-可见反射吸收光谱(UV-vis)对催化剂进行了初步表征. 通过X射线光电子能谱(XPS)、元素分析仪(EA)测定其含氮量. XPS分析结果显示TiO₂晶格中的氧被氮原子取代, N/TiO₂表面存在Ti^3＋离子; 紫外-可见反射吸收光谱测得不同掺杂量的N/TiO₂的禁带宽度(E_g), 推测在TiO₂价带上方生成了由N诱导产生的中间带, 当氮、钛摩尔比为0.0880时N/TiO₂的E_g最小, 为2.50 eV. 在可见光下, 以酸性桃红(SRB)和无色小分子对氯苯酚(4-CP)作为可见光活性实验的探针反应, 确定了最佳掺杂比为n_N/n_Ti＝0.0880. 结果表明, 最佳掺杂量下N/TiO₂能显著降解SRB和4-CP, 通过测定ESR, IR, TOC, COD, 重点比较了TiO₂在掺杂N前后在降解SRB和4-CP时的差异, 包括氧化物种、矿化率、最终产物等, 证明在可见光下, N/TiO₂的降解机理为电子从独立的N 2p轨道激发到Ti 3d轨道, 产生羟基自由基等氧化物种, 达到降解有机物的目的.     

Engineering of SnO2/TiO2 heterojunction compact interface with efficient charge transfer pathway for photocatalytic hydrogen evolution

Fabricating an efficient charge transfer pathway at the compact interface between two kinds of semiconductors is an important strategy for designing hydrogen production heterojunction photocatalysts. In this work, we prepared a compact, stable and oxygen vacancy-rich photocatalyst (SnO₂/TiO₂ heterostructure) via a simple and reasonable in-situ synthesis method. Briefly, SnCl₂–2H₂O is hydrolyzed on the TiO₂ precursor. After the pyrolysis process, SnO₂ nanoparticles (5 nm) were dispersed on the surface of ultrathin TiO₂ nanosheets uniformly. Herein, the heterojunction system can offer abundant oxygen vacancies, which can act as active sites for catalytic reactions. Meanwhile, the interfacial contact of SnO₂/TiO₂ grading semiconductor oxide is uniform and tight, which can promote the separation and migration of photogenerated carriers. As shown in the experimental results, the hydrogen production rate of SnO₂/TiO₂ is 16.7 mmol h^?1 g^?1 (4.4 times higher than that of TiO₂), which is owing to its good dynamical properties. This work demonstrates an efficient strategy of tight combining SnO₂/TiO₂ with abundant oxygen vacancies to improve catalytic efficiency.     

Quantitative XAFS/EELS analyses of nitrogen species in titanium oxide photocatalysts

With a view to rational designing of a highly functional visible-light TiO₂ photocatalyst, nitrogen atoms were doped into TiO₂ samples by an ion implantation technique which enables to control the depth and concentration of dopants. Although the absorbance in the visible-light region of the sample increased by the nitrogen doping, photocatalytic activity of the sample was not directly connected with the photo-absorbance. The N K-edge X-ray absorption near edge structure (XANES) spectrum of the photocatalytic active sample (A-cat) showed a characteristic double peak at 398 and 401 eV, and the XANES spectrum of the inactive sample (I-cat) a distinct single peak around 401 eV. These features of the XANES spectra were well reproduced by theoretical simulations based on the model where an O atom in TiO₂ was replaced by N ((N)s) for A-cat, and that of quasi NO₂ molecule ((NO₂)s) for I-cat. Therefore, we have concluded that the nitrogen atom occupying the oxygen site of TiO₂ is photocatalytic active species effective for visible light photocatalysis. In addition, the quantitative XANES/ELNES analysis has revealed that the photo-absorbance ratio of I-cat to A-cat corresponds well to the ratio of total doped nitrogen concentration rather than photocatalytic active nitrogen ((N)s) concentration. This result indicates that not only (N)s but also (NO₂)s also absorb the visible light. Thus, the absorbance in the visible-light region is not necessarily an indication of the visible-light response of a photocatalyst.