Preparation and characterization of nano TiO2/micron Cr2O3 composite particles

Nano-TiO₂/micro-size Cr₂O₃ composite particles were first prepared by hydrolysis of Ti(OBu)₄ in an abundant acidic aqueous solution without calcinations at room temperature. XPS analysis shows that the element C, O, Ti and Sn existed on the surfaces of the composite particles. Observation by field emission scanning electronic microscope shows TiO₂ particles of 10-15 nm covers on Cr₂O₃ powder surfaces to form nanometer/micron composite particles. UV-vis spectra show a red shift of the absorption edge and a significant increase of absorption intensity in the visible region. These results confirm that TiO₂ of anatase type can be synthesized on the surface of Cr₂O₃.     

NiMoO4/g-C3N4的制备及电化学性能研究

超级电容器具有比电容高、循环寿命长和绿色无污染的特点,其优异的电化学性能备受关注。本文水热合成了NiMoO₄/g-C₃N₄复合粉体,并将粉体涂覆在泡沫镍上制备了NiMoO₄/g-C₃N₄电极材料。结果表明,NiMoO₄/g-C₃N₄粉体形貌主要为NiMoO₄纳米棒和团状g-C₃N₄,且NiMoO₄纳米棒生长在g-C₃N₄纳米片上。在NiMoO₄中加入30at%的g-C₃N₄能降低电容体系的等效串联电阻和扩散阻抗,有利于氧化还原反应的进行。相比于其他g-C₃N₄含量的电极材料,g-C₃N₄含量为30at%的NiMoO₄/g-C₃N₄电极材料具有更高的比电容(584.3F/g)和更好的倍率特性。     

Photocatalytic performance of nano-photocatalyst from TiO2 and Fe2O3 by mechanochemical synthesis

Nano-particles of homogeneous solid solution between TiO₂ and Fe₂O₃ (up to 10 mol%) have been prepared by mechanochemical milling of TiO₂ and yellow Fe₂O₃/red Fe₂O₃/precipitated Fe (OH)₃ using a planetary ball mill. Such novel solid solution cannot be prepared by conventional co-precipitation technique. A preliminary investigation of photocatalytic activity of mixed oxide (TiO₂/Fe₂O₃) on photo-oxidation of different organic dyes like Rhodamine B (RB), Methyl orange (MO), Thymol blue (TB) and Bromocresol green (BG) under visible light (300-W Xe lamp; λ > 420 nm) showed that TiO₂ having 5 mol% of Fe₂O₃ (YFT1) is 3-5 times higher photoactive than that of P25 TiO₂. The XRD result did not show the peaks assigned to the Fe components (for example Fe₂O₃, Fe₃O₄, FeO₃, and Fe metal) on the external surface of the anatase structure in the Fe₂O₃/TiO₂ attained through mechanochemical treatment. This meant that Fe components were well incorporated into the TiO₂ anatase structure. The average crystallite size and particle size of YFT1 were found to be 12 nm and 30 ± 5 nm respectively measured from XRD and TEM conforming to nanodimensions. Together with the Fe component, they absorbed wavelength of above 387 nm. The band slightly shifted to the right without tail broadness, which was the UV absorption of Fe oxide in the Fe₂O₃/TiO₂ particle attained through mechanochemical method. This meant that Fe components were well inserted into the framework of the TiO₂ anatase structure. EPR and magnetic susceptibility show that Fe³⁺ is in low spin state corresponding to μ_B = 1.8 BM. The temperature variation of μ_B shows that Fe³⁺ is well separated from each other and does not have any antiferromagnetic or ferromagnetic interaction. The evidence of Fe³⁺ in TiO₂/Fe₂O₃ alloy is also proved by a new method that is redox titration which is again support by the XPS spectrum.     

Modification of TiO2 nanorods by Bi2MoO6 nanoparticles for high performance visible-light photocatalysis

In this work, TiO₂ nanorods were prepared by a hydrothermal process and then Bi₂MoO₆ nanoparticles were deposited onto the TiO₂ nanorods by a solvothermal process. The nanostructured Bi₂MoO₆/TiO₂ composites were extensively characterized by X-ray diffraction, scanning and transmission electron microscopy, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance spectroscopy. The photocatalytic activity of the Bi₂MoO₆/TiO₂ composites was evaluated by degradation of methylene blue. The Bi₂MoO₆/TiO₂ composites exhibit higher catalytic activity than pure Bi₂MoO₆ and TiO₂ for degradation of methylene blue under visible light irradiation (λ > 420 nm). Further investigation revealed that the ratio of Bi₂MoO₆ to TiO₂ in the composites greatly influenced their photocatalytic activity. The experimental results indicated that the composite with Bi₂MoO₆:TiO₂ = 1:3 exhibited the highest photocatalytic activity. The enhancement mechanism of the composite catalysts was also discussed.     

Effect of Nd2O3 addition on the surface phase of TiO2 and photocatalytic activity studied by UV Raman spectroscopy

TiO₂ modified with Nd₂O₃ (Nd-TiO₂) nanoparticles were prepared by a co-precipitation method and utilized as the photocatalysts for the degradation of Rhodamine B (RhB). The influence of Nd₂O₃ on the bulk and surface phase, surface area, particle size, and optical response of TiO₂ was investigated by X-ray diffraction (XRD), UV Raman spectroscopy, transmission electron microscopy (TEM), BET, and UV-visible diffuse reflectance spectra. It is found that the crystalline phase and phase composition in the bulk and surface region of Nd-TiO₂ calcined at high temperatures can be tuned by changing the amount of Nd₂O₃. Based on the results from XPS, EDX, XRD, and UV Raman spectra, it is assumed that Nd³⁺ ions do not enter the TiO₂ lattice, but highly disperse onto the Nd-TiO₂ particle surface in the form of Nd₂O₃ crystallites. These crystallites inhibit the agglomeration, growth in crystal size, and anatase-to-rutile phase transformation of TiO₂. In the photocatalytic degradation of RhB reaction, Nd-TiO₂ nanoparticles with higher surface area and wider optical response are more reactive in case of the same surface anatase phase. When the mixed phases of anatase and rutile exist in the surface region of Nd-TiO₂, the synergetic effect over surface area and optical response is the important parameter which determines optimal photocatalytic activity.     

Fe3O4/SiO2/Bi2WO6磁性复合光催化剂的制备及其光催化性能

钨酸铋(Bi₂WO₆),结构最简单的Aurivillius相化合物,是近期受到研究者关注的新型光催化材料。然而,光催化剂粉末在反应介质中难被回收,工业化应用成本较高。本文用三步方法合成了可回收的Fe₃O₄/SiO₂/Bi₂WO₆磁性复合光催化剂,通过溶剂热法合成具有磁性的Fe₃O₄,用溶胶凝胶法在Fe₃O₄表面覆盖SiO₂层,后将磁性颗粒与Bi₂WO₆纳米片相结合。光催化剂的形貌结构及性能通过XRD、SEM、PL、UV-vis进行表征测试。结果表明,直径约500 nm的Fe₃O₄微球附着在边长约500 nm的Bi₂WO₆纳米片的表面,SiO₂在两者之间起到了粘连作用。光催化剂Fe₃O₄/SiO₂/Bi₂WO₆对于罗丹明B的光降解活性较好,且有一定磁性,可以通过外加磁场将其从溶液中分离,有较大的应用潜力。     

Fe掺杂TiO2纳米材料的合成及光催化性能

以钛酸丁酯为钛源,Fe(NO3)3·9H2O为铁源,采用溶胶-凝胶法制备Fe/TiO2纳米粉体,利用溶胶结合静电纺丝技术制备Fe/TiO2纳米纤维,从材料改性及形貌改善两个角度共同提高TiO2纳米材料的光催化活性及实用性。借助XRD、SEM、TEM等分析技术,探究了Fe/TiO2纳米材料在可见光区的光催化活性,分析了煅烧温度及掺铁量对Fe/TiO2纳米材料光催化性能的影响。结果显示,铁的掺入及形貌的改善有助于提高TiO2的光催化性能。     

Electrodeposition of sol-enhanced nanostructured Ni-TiO2 composite coatings

A novel electroplating method has been developed to produce nanocrystalline metal-matrix nano-structured composite coatings. A small amount of transparent TiO₂ sol was added into the traditional electroplating Ni solution, leading to the formation of nanocrystalline Ni-TiO₂ composite coatings. These coatings have a smooth surface. The Ni nodules changed from traditional pyramid-like shape to spherical shape. The grain size of Ni was also significantly reduced to the level of 50 nm. It was found that the amorphous anatase TiO₂ nano-particles (∼ 10 nm) were highly dispersed in the coating matrix. The microhardness was significantly increased from 320 HV₁₀₀ of the traditional Ni coating to 430 HV₁₀₀ of the novel composite coating with 3.26 wt.% TiO₂. Correspondingly, the wear resistance of the composite coating was improved by ∼ 50%.     

Characteristics of N-doped TiO2 nanotube arrays by N2-plasma for visible light-driven photocatalysis

N-doped TiO₂ nanotube arrays were prepared by electrochemical anode oxidation of Ti foil followed by treatment with N₂-plasma and subsequent annealed under Ar atmosphere. The morphologies, composition and optical properties of N-doped TiO₂ nanotube arrays were characterized using field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction spectrometer (XRD), Photoluminescence (PL) and UV-vis diffusion reflection spectroscopy (UV-vis DRS). Methylene blue (MB) solution was utilized as the degradation model to evaluate the photocatalytic activity of the samples under visible light irradiation. The results suggested N₂-plasma treatment created doping of nitrogen onto the surface of photoelectrodes successfully and the N-doped TiO₂ nanotube arrays display a significantly enhancement of the photocatalytic activity comparing with the pure TiO₂ nanotube arrays under the visible light irradiation.     

SnO2@TiO2核-壳纳米线的制备及其光催化性能研究

本文通过固-液-气(VLS)生长机制,利用化学气相沉积法(CVD)制备SnO₂纳米线。利用原子层沉积(ALD)以钛酸四异丙酯为前驱体在SnO₂纳米线表面沉积不同厚度的TiO₂壳层,形成SnO₂@TiO₂核-壳纳米线结构。通过中间Al₂O₃插层,分别制备出金红石和锐钛矿两种不同晶型的TiO₂,从而制备出两种不同复合结构的SnO₂@TiO₂核-壳纳米线。实验研究该复合结构中TiO₂的厚度与晶型对紫外光下光催化降解甲基橙溶液活性的影响。     

TiO2/膨润土复合光催化材料的常温制备及性能研究

采用改进的溶胶-凝胶法,在以水为主要溶剂的反应体系中,控制钛酸四丁酯充分水解、缓慢聚合,在 常压、低温(70℃)的温和条件下制备出稳定的TiO₂纳米晶溶胶,并利用TiO₂纳米晶溶胶在膨润土表面负载,获得TiO₂/膨润土复合光催化材料。采用 X 射线衍射、扫描电镜、比表面积测定等研究手段对样品的结构形貌进行了表征,并考察了其光催化活性。结果表明：较高的水用量有利于TiO₂晶体形成,当去离子水:钛酸四丁酯摩尔比大于167:1时,在溶胶体系中出现了锐钛矿型TiO₂纳米晶体;TiO₂纳米晶主要负载于膨润土表面,并未嵌入到膨润土层间结构,但相对于单一膨润土,TiO₂负载显著提高了材料比表面积;当去离子水:钛酸四丁酯摩尔比=192:1时,在紫外光照射下,复合光催化材料表现出最高的光催化活性,对亚甲基蓝的降解率达到93.8%。     

Effect of Nb doping on the phase transition and optical properties of sol-gel TiO2 thin films

Various content Nb-doped TiO₂ thin films were prepared by sol-gel process. XRD analysis shows that the existence of crystalline TiO₂ in anatase and rutile form depends on the Nb content in the examined samples. It is observed that Nb promotes the anatase to rutile phase transition but has a depression effect on the anatase grain growth. It is found that incorporation of about 4 at.% of Nb completely transforms anatase TiO₂ to the rutile form at a calcination temperature as high as 900 °C. The mechanism is proposed. Optical analyses show that the films have an average of 60% transmission in visible region. The energy gap values using Tauc's formula have also been estimated. The band gap of rutile Ti_1−xNb_xO₂ solid solutions increases with increasing x.     

Synthesis of WO3 nanoparticles for photocatalytic O2 evolution by thermal decomposition of ammonium tungstate loading on g-C3N4

Tungsten trioxide (WO₃) nanoparticles have been successfully synthesized by thermal decomposition of ammonium tungstate loading on g-C₃N₄. The as prepared nanoparticles were characterized by XRD, UV-vis, photoluminescence spectra (PL) and TEM. The XRD results indicate that the g-C₃N₄ decomposed completely with WO₃ remaining at calcination temperature higher than 550 °C. The WO₃ prepared at temperature below 750 °C exhibits orthorhombic phase, and monoclinic phase at temperature higher than 850 °C. The UV-vis absorption onset wavelength of the obtained samples is approximately 470 nm, and the absorption intensity increases with calcination temperature, and reaches a maximum at 750 °C. The as prepared WO₃ powders, loaded with 0.5 wt% Pt as cocatalyst, were used as photocatalysts for O₂ evolution from an aqueous KIO₃ solution. The WO₃ nanoparticles prepared from ammonium tungstate loading on g-C₃N₄ showed photocatalytic activity in O₂ evolution up to 77 times higher than that of WO₃ samples prepared from ammonium tungstate without loading on g-C₃N₄.     

First-principles study on the electronic and optical properties of F- and Nb-doped anatase TiO2

We present a comparative study on the electronic and optical properties of Nb- and F- doped anatase TiO₂ by first-principles calculations based on the density functional theory (DFT). Although both TiO₂:Nb and TiO₂:F have a similar band structure, the effective mass of TiO₂:F is larger than that of TiO₂:Nb, and the carriers density in the former is lower than that in the latter, indicating that TiO₂:Nb has better electronic conductivity than TiO₂:F. The interaction between photons and electrons in TiO₂:F is much stronger than that in TiO₂:Nb, resulting in increased photon absorption and reduced transmittance, especially in the visible and near-infrared regions. The results demonstrate that TiO₂:F is not suitable for transparent conductive oxide applications.     

废旧锂离子电池中Li, Fe和V的回收及xLiFePO4-yLi3V2(PO4)3的制备

由于LiFePO_4和Li_3V_2(PO_4)_3材料的特征相近,制备方法类似,提供了一种从废旧LiFePO_4和Li_3V_2(PO_4)_3混合电池中回收Li、Fe和V,再制备xLiFePO_4-yLi_3V_2(PO_4)_3的方法。在空气气氛中600℃热处理1h后,去除粘结剂PVDF使活性物质与集流体分离。调节Li、Fe、V和P摩尔比,球磨、锻烧,配制不同比例的xLiFePO_4-yLi_3V_2(PO_4)_3(x:y=5:1,7:1,9:1)复合电极材料。表征了其形貌、结构和电化学性能,结果表明,回收制备的复合材料将同时具备LiFePO_4和Li_3V_2(PO_4)_3两种材料的电化学性能,能显著改善LiFePO_4的倍率性能。     

Spectroscopic and crystal-field analysis of energy levels of Eu in SnO2 in comparison with ZrO2 and TiO2

We have carried out systematic crystal-field energy level calculations of Eu³⁺ ions doped in SnO₂ based on experimentally acquired luminescence spectra. In addition, with an aim of revealing systematic trends in spectra and crystal-field effects for Eu³⁺ ion in similar hosts, we have analyzed the TiO₂ (anatase):Eu³⁺ spectra as well. The obtained crystal-field parameters yield very good agreement between the calculated and observed energy levels. Emphasis has been put on analysis of the crystal-field-induced J-mixing effects and their roles in getting proper sets of crystal-field parameters and energy levels. A more general theory concerning J-mixing effects has been proposed and the relevant results will be valuable to understanding of the spectral characteristics of Eu³⁺ f-f transition spectra in other hosts. Relations between the maximum crystal-field splitting of some selected J-manifolds with J = 1 and J = 2 and crystal-field invariants have been re-visited and re-derived. The corresponding numbers of crystal-field parameters influencing the splitting of these manifolds have been taken into account in every case. The derived equations have been tested in applications to three systems (SnO₂, TiO₂ (three sites) and ZrO₂). Consistent results have been obtained, which confirms validity of the performed crystal-field analysis and opens a way for possible applications of the suggested calculating technique to other rare-earth ions.     

无模板剂的溶胶-水热法合成具有可见光响应的氮掺杂混晶 TiO2(锐钛矿/金红石/板钛矿)纳米棒束

采用无模板剂的溶胶-水热法制备了具有可见光响应的N掺杂锐钛矿/金红石/板钛矿型TiO_2(N-TiO_2)纳米棒束,并利用X射线衍射(XRD)、透射电镜(TEM)、紫外-可见光漫反射光谱(UV-Vis DRS)、傅里叶变换红外光谱(FTIR)和X射线光电子能谱(XPS)等手段对获得的样品进行了表征。以甲基橙为模型反应物,评价了N-TiO_2纳米棒束的光催化活性。表征结果结合光催化活性评价结果显示,与P25-TiO_2相比,N掺杂、混晶及纳米棒束之间的协同作用是所制备的混晶N-TiO_2纳米棒束具有良好光催化活性的主要原因,并对混晶N-TiO_2纳米棒束光催化降解甲基橙的机理进行了探讨。     

Preparation and characterization of spinel Li4Ti5O12 anode material from industrial titanyl sulfate solution

Spinel Li₄Ti₅O₁₂ anode material is successfully synthesized by a solid-state method using lithium carbonate and titanium precursors which are prepared by the low cost industrial titanyl sulfate solution. The characters of H₂TiO₃ and TiO₂ precursors are determined by TG/DTA and SEM methods. TG-DAT and EDS methods show that H₂TiO₃ can absorb sulphate ions which can be present as impurities. XRD method shows that the impure phases of Li₂SO₄ and rutile TiO₂ appear in Li₄Ti₅O₁₂ synthesized by H₂TiO₃. The formation of Li₂SO₄ is identified in thermodynamics during the process of calcination. Owing to the formation of Li₂SO₄ impurity, the capacity of the Li₄Ti₅O₁₂ synthesized by H₂TiO₃ is low. One effective way that can tackle this problem is to remove the sulphur by calcining H₂TiO₃, after calcinations, the production will have a thermal treatment with Li₂CO₃. The obtained Li₄Ti₅O₁₂ shows better electrochemical performance. The specific capacities can be increased by 20 mAh g⁻¹ at 0.1, 0.5 and 1C rates.     

Enhanced photocatalytic activity of TiO2 nanoparticles using WS2/g-C3N4 hybrid as co-catalyst

TiO₂/WS₂/g-C₃N₄ composite photocatalysts were synthesized by a liquid-exfoliation-solvothermal method. In this process, the WS₂/g-C₃N₄ nano-sheets were prepared by liquid-exfoliation method from the bulk WS₂ and C₃N₄ in the alcohol system, and then the TiO₂ nanoparticles (NPs) grew on the WS₂/g-C₃N₄ nano-sheets by in-situ synthesized technique. The photocatalytic activity of the as-prepared samples was evaluated by photocatalytic degradation of methyl orange (MO). The results showed that the as-prepared samples exhibited higher photocatalytic activities as compared to the pure TiO₂, g-C₃N₄ and TiO₂/g-C₃N₄ composite. The enhanced photocatalytic activities of TiO₂/WS₂/g-C₃N₄ photocatalysts could be attributed to the synergistic effect of heterostructure between TiO₂ NPs and WS₂/g-C₃N₄ nano-sheets, which could efficiently improve the separation of photogenerated electron/hole pairs and utilization efficiency of photons. The quenching tests of radicals indicated that ·O^?₂ had crucial effect on degradation of MO, which demonstrated that ·O^?₂ was the main active radical in photocatalytic reaction process.     

Deposition of TiO2 thin films on steel using a microwave activated chemical bath

Microwave activated chemical bath deposition (MW-CBD) is a simple and novel technique in which the substrate is heated directly by microwaves and very well adhered layers are obtained. It has not been used previously for TiO₂ deposition on metals. We show that it is possible to coat stainless steel with TiO₂ using MW-CBD. Two different precursor solutions are used for TiO₂ deposition on steel grade 316. TiO₂ thin films on steel substrates were characterized using SEM and Raman spectroscopy. Raman analysis showed that amorphous TiO₂ is obtained using the precursor solution based on TiOSO₄; however, films show anatase crystal structure when using the precursor solution based on (NH₄)₂TiF₆. Thermal treatment of the films improved crystallinity and also allowed iron diffusion from the steel substrate into the film. Crystalline phases that appeared due to heat treatment were identified from Raman spectra. MW-CBD allows simple low temperature coating of a metal substrate with TiO₂ and this should be useful for a number of different applications.