The effect of Sn dopant on crystal structure and photocatalytic behavior of nanostructured titania thin films

In this study, preparation of Sn doped (0–30 mol % Sn) TiO₂ dip-coated thin films on glazed porcelain substrates via sol–gel process have been investigated. The effects of Sn content on the structural, optical, and photo-catalytic properties of applied thin films have been studied by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), field emission SEM (FE-SEM), and high resolution transmission electron microscopy (HR-TEM). Surface topography and surface chemical state of thin films were examined by atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). XRD patterns showed an increase in peak intensities of the rutile crystalline phase by increasing the Sn dopant. The prepared Sn-doped TiO₂ photo-catalyst films showed optical absorption edge in the visible light area and exhibited excellent photo-catalytic ability for degradation of methylene blue solution under UV irradiation. The result shows that doping an appropriate amount of Sn can effectively improve the photo-catalytic activity of TiO₂ thin films, and the optimum dopant amount is found to be 15 mol%. The Sn⁴⁺ dopants substituted Ti⁴⁺ in the lattice of TiO₂ and increased surface oxygen vacancies and the surface hydroxyl groups. TEM results showed small increase in planar spacing (was detected by HR-TEM caused by Sn dopants in titania based crystals).     

Enhanced photoinduced super-hydrophilicity in sol–gel TiO2 thin films with co-doped Sn/Nb

In this work, Sn and Nb co-doped TiO₂ were coated on glazed porcelain substrates via sol–gel dip coating method. Field emission-scanning electron microscopy, transmission electron microscopy, and UV–vis spectrophotometer were used to evaluate thickness and optical properties of the thin films. Surface chemical state of thin films was examined by atomic X-ray photoelectron spectroscopy. Water contact angle on the film surfaces was measured by a contact angle analyzer under solar light irradiation. The optical results indicated that Sn/Nb dopant in TiO₂ thin film changed the absorption edge from ultraviolet to visible light and exhibited excellent photo-catalytic ability for degradation of methylene blue solution under solar irradiation. Wettability results indicated that Sn and Nb dopant ions had significant effect on the hydrophilicity property of thin films.     

Comparison of optical and structural properties of nanostructure TiO2 thin film doped by Sn and Nb

The thin films of TiO₂ doped by Sn or Nb were prepared by sol–gel method under process control. The effects of Sn and Nb doping on the structural, optical and photo-catalytic properties of applied thin films have been studied by X-ray diffraction (XRD) high resolution transmission electron microscopy and UV–Vis absorption spectroscopy. Surface chemical state of thin films was examined by atomic X-ray photoelectron spectroscopy. XRD results suggest that adding impurities has a great effect on the crystallinity and particle size of TiO₂. Titania rutile phase formation in thin film was promoted by Sn⁴⁺ addition but was inhibited by Nb⁵⁺ doping. The activity of the photocatalyst was evaluated by photocatalytic degradation kinetics of aqueous methylene blue under UV and Visible radiation. The results show that the photocatalytic activity of the Sn-doped TiO₂ thin film have a larger degradation efficiency than Nb-doped TiO₂ under visible light, but under UV light photocatalytic activity of the Nb-doped TiO₂ thin film is better.     

High temperature stability and photocatalytic activity of nanocrystalline anatase powders with Zr and Si co-dopants

TiO₂ nanopowders doped by Si and Zr were prepared by sol–gel method. The effects of Si and Zr doping on the structural, optical, and photo-catalytic properties of titania nanopowders have been studied by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and UV–Vis absorption spectroscopy. XRD results suggest that adding impurities has a significant effect on anatase phase stability, crystallinity, and particle size of TiO₂. Titania rutile phase formation in ternary system (Ti–Si–Zr) was inhibited by Zr⁴⁺ and Si⁴⁺ co-doped TiO₂ in high temperatures (500–900 °C) and 36 mol% anatase composition is retained even after calcination at 1,000 °C. The photocatalyst activity was evaluated by photocatalytic degradation kinetics of aqueous methylen orange under visible radiation. The results show that the photocatalytic activity of the 20 %Si and 15 %Zr co-doped TiO₂ nanopowders have a larger degradation efficiency than pure TiO₂ under visible light.     

Vacuum activation-induced Ti<Superscript>3+</Superscript> and carbon co-doped TiO<Subscript>2</Subscript> with enhanced solar light photo-catalytic activity

Ti³⁺ and carbon co-doped TiO₂ photocatalysts were prepared hydrothermally to introduce the carbon, and followed by simple vacuum activation to achieve the Ti³⁺ self-doping. The prepared co-doped photocatalysts were characterized by XRD, TEM, UV–Vis absorption spectra, EPR, and XPS. It was found that the co-doped TiO₂ has dispersed nanoparticles and a narrower band-gap compared with the un-doped TiO₂ and single-doped TiO₂. The experimental results displayed that the coke carbon generated on the surface of co-doped TiO₂ acts as a photosensitizer and has the photosensitization effect under solar light irradiation. Except for the carbon sensitization effect, the Ti³⁺ self-doping modification has a synergistic effect which is the reason for the effective photo-degradation of methyl orange under simulated solar light irradiation.     

Preparation and characterization of silver and indium vanadate co-doped TiO2 thin films as visible-light-activated photocatalyst

Novel visible-light-activated photocatalytic Ag/InVO₄-TiO₂ thin films were developed in this paper through a sol-gel method from the TiO₂ sol containing Ag and InVO₄. The photocatalytic activities of Ag/InVO₄-TiO₂ thin films were investigated based on the oxidation decomposition of methyl orange in aqueous solution. The Ag/InVO₄-TiO₂ thin films were characterized by X-Ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and UV-vis absorption spectroscopy (UV-vis). The results revealed that the Ag/InVO₄-TiO₂ thin films extended the light absorption spectrum toward the visible region; the Ag and InVO₄ co-doped thin films significantly enhanced the methyl orange photodegradation under visible light irradiation. It has been confirmed that the Ag/InVO₄-TiO₂ thin films could be excited by visible light (E < 3.2 eV). The significant enhancement in the Ag/InVO₄-TiO₂ photo activity under visible light irradiation can be ascribed to the simultaneous effects of doped noble metal Ag by acting as electron traps and InVO₄ as narrow band gap sensitizer.     

具有高可见光催化活性的Ti3+和碳共掺杂改性的TiO2光催化剂

以乙醇为碳源,采用操作简单的真空活化法一步实现对TiO₂的Ti³⁺与C的共掺杂改性,TiO₂用X衍线衍射、紫外-可见光谱、顺磁共振、X射线光电子能谱和红外光谱等手段表征了催化剂的结构、组成、光学性质. 结果表明, 经Ti³⁺与C共掺杂改性后的催化剂表现出高的可见光降解甲基橙活性. 复合在催化剂表面的石墨可以增强催化剂对可见光的响应范围,而Ti³⁺与氧缺陷形成的掺杂能级则可以提高光生电子的迁移效率. 实验表明,两者之间的协同作用促进了其可见光催化活性的提高.     

Photovoltaic Behaviour of Titanyl Phthalocyanine Thin Films and Titania Bilayer Films

Summary: Titanyl phthalocyanine (TiOPc) thin films were prepared using evaporation and surface polymerization by ion-assisted deposition (SPIAD) in a vacuum deposition system. These films were characterized by means of ultraviolet and X-ray photoelectron spectroscopy as well as UV/Vis absorption spectroscopy. Valence band and elemental content indicated that phthalocyanine electronic and chemical structures were largely preserved during SPIAD. Further, bilayer thin films of titania (TiO₂) and SPIAD TiOPc were prepared. TiO₂ film was deposited by reactive magnetron sputtering of TiO₂ target. Study of the structured samples was focused on the optical and electrical properties of the composite films. The films were characterized by non-contact photovoltage measurements and UV-Vis spectroscopy. These results suggest there is a possibility to use these bilayer thin films in photovoltaic solar cells, however further experiments to improve conductivity of the films will be required.     

Photocatalytic activity of (sulfur,nitrogen)-codoped mesoporous TiO<Subscript>2</Subscript> thin films

Nitrogen and sulfur co-doped mesoporous TiO₂ thin films were fabricated using thiourea as a doping resource by the combination of the sol–gel and evaporation-induced self-assembly (EISA) processes. Scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N₂ adsorption–desorption, and UV–vis spectra were performed to characterize the as-synthesized mesoporous TiO₂ materials. The XPS result shows that O–Ti–N and O–Ti–S bonds in the (S, N)-codoped mesoporous TiO₂ were formed. The resultant mesoporous (S, N)-codoped TiO₂ exhibited anatase framework with a high porosity and a narrow pore distribution. After being illuminated for 3 h, methyl orange (MO) could be degraded completely by the co-doped sample under the ultraviolet irradiation, whereas mesoporous TiO₂ film without doping could only degrade 60% MO. After being illuminated by visible light, the water contact angles of the mesoporous co-doped TiO₂ samples decreased slightly, but the pure TiO₂ mesoporous film exhibited no change in the hydrophilicity.     

生物质C-N-P自掺杂TiO_2的合成及其对亚甲基兰的光催化降解活性

采用溶胶-超声辐照技术同步合成了生物质C-N-P自掺杂TiO_2复合催化剂,通过X射线光电子能谱(XPS)、X射线衍射(XRD)、扫描电子显微镜(FESEM)、紫外-可见漫反射光谱(UV-Vis-DRS)及光致发光光谱(PL)对样品进行了表征.以亚甲基兰(MB)为目标污染物,研究了C-N-P共掺杂TiO_2的可见光光催化性能.实验结果表明,在可见光照射下,光催化反应时间为2 h时,C-N-P共掺杂TiO_2复合催化剂对亚甲基兰的降解效率最高可达9 8.5%;相比纯TiO_2,C-N-P共掺杂TiO_2复合催化剂的比表面积增大,吸收边带红移,禁带宽度减小,相变温度升高,光生载流子复合率降低.     

Synthesis and characterization of novel InVO<Subscript>4</Subscript>–TiO<Subscript>2</Subscript> thin films using the low temperature sol

The InVO₄ sol was obtained by a mild hydrothermal treatment (the precursor precipitation solution at 423 K, for 4 h). Novel visible-light activated photocatalytic InVO₄–TiO₂ thin films were synthesized through a sol–gel dipping method from the composite sol, which was obtained by mixing the low temperature InVO₄ sol and TiO₂ sol. The photocatalytic activities of the new InVO₄–TiO₂ thin films under visible light irradiation were investigated by the photocatalytic discoloration of methyl orange aqueous solution. The thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and UV–Vis absorption spectroscopy (UV–Vis). The results revealed that the InVO₄ doped thin films enhanced the methyl orange degradation rate under visible light irradiation, 3.0 wt% InVO₄–TiO₂ thin films reaching 80.1% after irradiated for 15 h.     

Photocatalytic degradation of organic compounds in aqueous systems by Fe and Ho codoped TiO<Subscript>2</Subscript>

Undoped, single-doped, and codoped TiO₂ nanoparticles were prepared by the sol-gel method and characterized with X-ray diffraction (XRD), the Brunauer-Emmett-Teller (BET)-specific surface area (S_BET), UV-Vis absorption spectra (UV-Vis), and X-ray photoelectron spectroscopy (XPS). Their photocatalytic activity was evaluated by methyl orange (MO) degradation in an aqueous suspension under UV or simulated solar light illumination. XRD showed that all samples calcined at 600°C preserved the anatase structure, and doping inhibited the increase of crystallite size. The BET result revealed that doping improved the surface area of TiO₂. UV-Vis indicated that Fe³⁺-doping broadened the absorption profile of TiO₂. XPS demonstrated that doping was advantageous to absorb more surface hydroxyl groups or chemisorbed water molecules. Photocatalytic degradation showed that the photocatalytic activity of TiO₂ codoped with Fe³⁺ and Ho³⁺ ions was markedly improved. This was ascribed to the fact that there was a cooperative action in the two doped elements. Fe³⁺-doping broadens the absorption profile, improves photo utilization of TiO₂, and then generates more electronhole pairs. Ho³⁺-doping restrains the increase in grain size and retards the recombination of photo-generated electrons and holes.     

Synthesis and photocatalytic activity of nanocrystalline TiO2 co-doped with nitrogen and cobalt(II)

Nitrogen-modified cobalt-doped TiO₂ materials were successfully prepared via a modified sol–gel method. The structure and properties of the catalysts were characterized via X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM, ultraviolet–visible light diffuse reflectance spectra (UV–Vis DRS), N₂ adsorption–desorption isotherms, and energy-dispersive X-ray spectroscopy. The XRD patterns of the pure and co-doped TiO₂ samples indicate that the predominant phase was anatase. The average grain size obtained from TEM was approximately 10 nm. The Brunauer–Emmett–Teller analysis results indicate that the specific surface area was 77.7 m² g^?1. The UV–Vis DRS results for the co-doped sample reveal an absorption edge that had been red-shifted to 500 nm. The photocatalytic activities of the samples were evaluated through photodegradation of papermaking wastewater under UV and visible light irradiation. Compared with the cobalt-doped TiO₂ sample and Degussa P25, the 3 mol% N-doped mesoporous N/Co-TiO₂ photocatalyst exhibited the highest photocatalytic activity, which can be ascribed to the synergistic effect of the N and Co co-doping.     

Fabrication of highly efficient dye-sensitized solar cell and CO2 reduction photocatalyst using TiO2 nanoparticles prepared by spin coating-assisted sol–gel method

A sol?Cgel method was applied for fabrication of nanocrystalline anatase TiO₂ thin films on ITO glass substrates and followed by rapid thermal annealing for application as the work electrode for dye-sensitized solar cells (DSSC). TiO₂ nanoparticles were characterized by X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM) and the absorption of dye on the TiO₂ electrode was shown by UV?Cvis spectroscopy. By controlling different parameters including numbers of coated layers, the gap between two electrodes, sensitization time, and light source power, TiO₂-based solar cells with high efficiency was achieved. The results show that a five time spin-coated TiO₂ electrode with applying sealant and sensitization time of 24?h in N3 dye under illumination of 100?W?cm^?2 tungsten lamp give the optimum power conversion efficiency (??) of 6.61%. The increases in thickness of TiO₂ films by increasing the numbers of coated layers can improve adsorption of the N3 dye through TiO₂ layers to increase the open-circuit voltage (V _oc). However, short-circuit photocurrents (J _sc) of DSSCs with a one-coated layer of TiO₂ films are smaller than those of DSSCs with five-coated layer of TiO₂ films. It could be due to the fact that the increased thickness of TiO₂ thin films also resulted in a decrease in the transmittance of TiO₂ thin films. Also, this electrode was employed to photoreduce CO₂ with H₂O under tungsten lamp as light source.     

Preparation and photocatalytic activity of B,Ce Co-doped TiO2 hollow fibers photocatalyst

A series of B, Ce co-doped TiO₂ (B, Ce-TiO₂) photocatalytic materials with a hollow fiber structure were successfully prepared by template method using boric acid, ammonium ceric nitrate and tetrabutyltitanate as precursors and cotton fibers as template, followed by calcination at 500°C in an N₂ atmosphere for 2 h. Scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen adsorption-desorption measurements, and UV-visible spectroscopy (UV-Vis) were employed to characterize the morphology, crystal structure, surface structure, and optical absorption properties of the samples. The photocatalytic performance of the samples was studied by photodegradation phenol in water under UV light irradiation. The results showed that the TiO₂ fiber materials have hollow structures, and the fiber structure materials showed better photocatalytic properties for the degradation of phenol than pure TiO₂ under UV light. In the experiment condition, the photocatalytic activity of B, Ce co-doped TiO₂ fibers was optimal of all the prepared samples. In addition, the possibility of cyclic usage of B, Ce co-doped TiO₂ fiber photocatalyst was also confirmed, the photocatalytic activity of TiO₂ fibers remained above 90% of that of the fresh sample after being used four times. The material was easily removed by centrifugal separation from the medium. It can therefore be potentially applied for the treatment of water contaminated by organic pollutants.     

The Effect of SiO2 Addition on the Grain Size and Photocatalytic Activity of TiO2 Thin Films

The uniform transparent TiO₂/SiO₂ nanometer composite thin films were prepared via sol-gel method on the soda lime glass substrates, and were characterized by X-ray photoelectron spectroscopy (XPS), FTIR spectroscopy, UV-VIS spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET surface areas. It was found that the addition of SiO₂ to TiO₂ thin films could suppress the grain growth of TiO₂ crystal and increase the hydroxyl content of the surface of TiO₂ films. The photocatalytic activity of the as-prepared TiO₂/SiO₂ composite thin films increases for SiO₂ content of less than 5 mol%.     

Ag@AgI/Ni薄膜的制备及其模拟太阳光催化性能

采用电化学方法制备Ag@AgI/Ni表面等离子体薄膜催化剂,使用扫描电镜（SEM）,X射线衍射（XRD）和紫外-可见漫反射光谱（UV-Vis DRS）对薄膜的表面形貌、晶体结构、光谱特性以及能带结构进行分析表征,在模拟太阳光照射下,把罗丹明B作为模拟污染物对薄膜的光催化活性与稳定性进行评价,采用向反应体系中加入活性物种捕获剂的方法对薄膜光催化机理进行探究。结果表明：最佳工艺下制备的Ag@AgI/Ni薄膜表面是由附着少量Ag粒子的AgI纳米晶构成。薄膜具有显著的表面等离子共振作用、优异的光催化活性和突出的光催化稳定性。光催化反应60 min,薄膜对罗丹明B的降解率（81.1%）是AgI/Ni薄膜的1.35倍,是TiO₂（P25）/ITO薄膜的1.61倍。在薄膜光催化活性基本保持不变的前提下可循环使用5次。薄膜表面纳米Ag的等离子共振对光阴极反应的活化是光催化性能提高的重要原因。提出了薄膜光催化降解罗丹明B的反应机理。     

Photocatalytic Activity and Characterization of the Sol-Gel Derived Pb-Doped TiO2 Thin Films

Photocatalytically active Pb-doped TiO₂ thin films were prepared on a soda-lime glass substrate by sol-gel dip-coating technique using TiO₂ sols containing lead(II) nitrate. The thin films were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), UV-VIS spectroscopy and X-ray diffraction (XRD). A shift of the UV-VIS absorption towards longer wavelengths was observed, which indicated a decrease in the band-gap of TiO₂ upon Pb doping. XRD results showed both pure and Pb-doped TiO₂ thin films were polycrystalline, anatase type, and oriented predominantly to the (101) plane. A slight shift in the d-spacing for the Pb-doped film indicated the incorporation of Pb into the TiO₂ lattice to form Pb _x Ti_1–x O₂ solid solution. AFM results showed Pb-doped TiO₂ thin films were composed of larger TiO₂ particles and had rougher surface, compared with un-doped TiO₂ thin films. XPS results showed that except for the enrichment of Pb near the surface, Pb exists in the forms of Pb _x Ti_1–x O₂ and PbO. Dimethyl-2,2-dichlorovinyl phosphate (DDVP) was efficiently degraded in the presence of the Pb-doped TiO₂ thin films by exposing the insecticide solution to sunlight. The mechanism of photocatalytic activity enhancement of the Pb-doped TiO₂ thin films was discussed.     

Ag@AgI/Ni薄膜的制备及其模拟太阳光催化性能

采用电化学方法制备Ag@AgI/Ni表面等离子体薄膜催化剂,使用扫描电镜(SEM),X射线衍射(XRD)和紫外-可见漫反射光谱(UV-Vis DRS)对薄膜的表面形貌、晶体结构、光谱特性以及能带结构进行分析表征,在模拟太阳光照射下,把罗丹明B作为模拟污染物对薄膜的光催化活性与稳定性进行评价,采用向反应体系中加入活性物种捕获剂的方法对薄膜光催化机理进行探究。结果表明:最佳工艺下制备的Ag@AgI/Ni薄膜表面是由附着少量Ag粒子的AgI纳米晶构成。薄膜具有显著的表面等离子共振作用、优异的光催化活性和突出的光催化稳定性。光催化反应60 min,薄膜对罗丹明B的降解率(81.1%)是AgI/Ni薄膜的1.35倍,是TiO_2(P25)/ITO薄膜的1.61倍。在薄膜光催化活性基本保持不变的前提下可循环使用5次。薄膜表面纳米Ag的等离子共振对光阴极反应的活化是光催化性能提高的重要原因。提出了薄膜光催化降解罗丹明B的反应机理。