Synthesis and characterization of visible light responsive N-TiO2 mixed crystal by a modified hydrothermal process

N doped TiO₂ with anatase and rutile mixed crystal were prepared by using tetrabutyl titanate as the precursor via a modified hydrothermal process and calcination at 320 °C. The microstructure and morphology of samples were characterized by XRD, UV-vis-DRS, FTIR and XPS. The results showed that N-TiO₂ particles were crystallized to anatase and rutile mixed crystal structure; they were presented narrow particle size distribution, and the average particle size was ca. 13.5 nm calculated from XRD results. It was found that the N-doped TiO₂ particles showed strong visible-light absorption and high photocatalytic activity for the mineralization of Rhodamine B under irradiation by visible light (400-500 nm). The high visible-light photocatalytic activity of the obtained N-doped TiO₂ might result from the synergetic effect of nitrogen doping and the mixed lattice structure of N-TiO₂. Possible mechanism of N-TiO₂ mixed crystal formed under hydrothermal conditions was discussed.     

稀土Sm掺杂对纳米TiO2结构和可见光催化性能的影响

采用溶胶-凝胶法制备了纯TiO2和稀土Sm掺杂TiO2纳米粉体( Sm-TiO2),通过XRD、XPS、FT-IR、UV-Vis-DRS、PL和Nano-sizer纳米粒度仪等对样品进行表征,以亚甲基蓝( MB)的光催化降解为探针反应,探讨稀土Sm掺杂对纳米TiO2的结构和可见光催化性能的影响。结果表明,Sm掺入TiO2后在表面存在Sm3+和Sm2+两种价态, Sm掺杂抑制了TiO2从锐钛矿向金红石的相转变,阻碍纳米晶粒生长,增加了纳米粉体表面羟基含量;适量的Sm掺杂能使TiO2吸收光谱的阈值波长红移,有效降低光生e-/h+的复合率,提高TiO2光催化活性。热处理温度500℃时,掺杂1.0wt;Sm的纳米TiO2样品在普通日光灯下对MB在6 h内的光催化降解效率达97;,明显高于同等条件下Degussa公司产品P25的降解率56;。     

Sm,C掺杂改性纳米TiO2及其可见光催化性能研究

通过溶胶-凝胶法制备了Sm、C分别单掺杂和共掺杂纳米TiO2光催化剂,采用XRD、FESEM、TEM、XPS、UV-Vis-DRS、PL、Nano-sizer纳米粒度分析仪等对样品进行表征,以光催化降解亚甲基蓝(MB)作为评价模型,研究了不同样品对MB的光催化降解效果.结果表明,Sm单掺杂抑制了TiO2从锐钛矿向金红石的相转变,抑制晶粒长大,C的单掺杂则促进了TiO2的相转变,Sm或(和)C的掺杂均能细化TiO2晶粒,拓展TiO2在可见光区的光谱响应范围,降低光生e-/h+对的复合几率.Sm、C的掺杂均能有效提高TiO2的光催化活性,且共掺杂时存在协同效应,当n(Sm)∶n(C)∶n(Ti)=0.01∶0.3∶1、热处理温度500 ℃时,Sm/C-TiO2样品在普通日光灯下催化降解MB的一级表观速率常数是相同条件下纯TiO2的4.3倍.     

UV-vis辐照下H2Fe2Ti3O10/TiO2插层材料光催化活性的研究

在高压汞灯辐照下,通过插入反应将H2Fe2Ti3O10与n-C3H7NH2/C2H5OH和TiO2溶胶制备出H2Fe2Ti3O10/TiO2插层复合物.插入TiO2的层状钙钛矿化合物H2Fe2Ti3O10在UV-vis辐照下表现出高活性.实验结果表明H2Fe2Ti3O10/TiO2作为光催化剂在可见光(λ＞420nm)下辐照24h,降解甲基橙的速率为59.0;.与相同条件下降解率只有24;的商用光催化剂TiO2(Degussa P-25)相比,H2Fe2Ti3O10/TiO2表现出了更高的光催化活性.     

异质结光催化剂PANI/F-BiPO4的制备及其可见光催化活性研究

采用简单的水热法结合化学吸附法制备了具有异质结构的光催化剂PANI/F-BiPO4,采用X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、紫外-可见漫反射光谱仪(DRS)、X射线光电子能谱仪(XPS)等对其结构、形貌、光谱特征、表面化学组成等进行了表征和分析.在可见光条件下,考察了PANI/F-BiPO4对罗丹明B(RhB)的光催化降解效率,并且对光催化降解的机理进行了分析.这种异质结构明显拓宽光吸收范围,同时PANI和F-BiPO4间载流子的有效迁移产生了内建电场,从而促进了光生电子与空穴的分离.研究表明:PANI/F-BiPO4在可见光下表现出优异的光催化活性.经可见光照射4 h,它对40 mg/L的RhB去除率达到98.7;.     

Incorporation of Lithium into TiO2 Host and its Application in Photocatalysis

Abstract

In this work we prepared the stable photocatalyst by the incorporation of lithium into TiO₂ host. Lithium hydroxide was used as the modifier. Titanium host material was in two forms: commercial titanium dioxide (anatase. Police Chemical Factory, Poland) and titanium slurry that was slightly crystallized. The prepared materials have been characterized by XRD. FTIR and UV-Vis/DR methods. The XRD analysis showed that the main component of these samples was lithium titanate—Li₂TiO₃. The photocatalytic activity of prepared materials was tested in the photocatalytic reactions of oil and phenol decomposition in water. It was found that both oil and phenol undergo the photocatalytic decomposition over lithium-TiO₂ and the activity of these materials was higher in comparison with that of pure anatase host.     

Highly efficient photocatalytic degradation of methyl orange and Rhodamine B by hierarchical BiOBr microspheres

Hierarchical BiOBr microspheres were successfully synthesized via a solvothermal method by using the diethylene glycol(DEG) as the solvent and soft‐template. The as‐obtained products were characterized by X‐ray powder diffraction (XRD), scanning electron microscopy (SEM), selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM), N₂ adsorption–desorption and UV–Vis diffuse reflectance spectroscopy(DRS) techniques. The formation mechanism for the growth of hierarchical BiOBr microspheres has been studied. The possible mechanism of photocatalysis has been discussed. Remarkably, the as‐prepared BiOBr microspheres has a large specific surface area, which can reach a maximum surface area of 55.9307 m²/g. In addition, the superior enhanced photocatalytic activities of BiOBr microspheres were evaluated by the photodegradation of methyl orange (MO) and Rhodamine B (RhB) under visible‐light illumination, which presented the efficiency up to 98.10% just within 50 min and 98.64% within 30 min, respectively. BiOBr microspheres can be a promising candidate as highly efficient photocatalyst for decompositing of organic contaminants for environmental remediation.     

Preparation and characterization of a novel solid titania precursor

Titania (TiO₂) is an important metal-oxide semiconductor and has a broad range of industrial applications in areas including pigment, photocatalysts, solar cells, ceramics, inorganic membranes, sensors, nonlinear optics and environmental purification, etc. Titania is often prepared using titania precursors. Here we report preparation of a novel solid titania precursor using a simple synthetic method, with a general chemical formula of TiSO₄(AcAc)_2−n(OH)_n · mH₂O (n < 2 and m < 2), that possesses high stability against hydrolysis and can be very conveniently employed for preparation of fine titania particles with no need of any solvent. Well dispersed TiO₂ nanoparticles with an average size of about 20 nm are prepared by directly annealing the solid titania precursor at 600 °C for 2 h. Characterization of the new solid titania precursor is carried out using transmission electron microscopy (TEM), thermogravimetry (TGA), Fourier transform infrared spectrometer (FT-IR) and X-ray diffractometer (XRD).     

Optical and Photocatalytic properties of Mn‐doped CuO nanosheets prepared by hydrothermal method

Mn‐doped CuO nanosheets were prepared through a hydrothermal method to enhance their photocatalytic property. The structural and morphological features were monitored by using X‐Ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) with energy dispersive spectroscopy (EDS). UV‐vis absorption spectra showed the enhance absorption performance both in UV and visible light region. The band gaps were also calculate and the minimum value was 1.25 eV. The photocatalytic activity was investigated by the degradation of methylene blue (MB), which indicated that the photoactivity of samples depended on the amount of Mn²⁺ incorporated into the CuO lattice. The improved performance of photocatalysts can be attributed to enhanced light absorption and lower electron‐hole recombination.     

A study about the stabilization of anatase phase at high temperatures on sol-gel cerium and copper doped titania and titania-silica powders

Copper and cerium oxides doped titania samples, as well as silica-titania samples were prepared through sol-gel process by using titanium butoxyde as precursor. The obtained samples were characterized by X-ray diffractometry and scanning electron microscopy. The main objective of the proposed study is to promote the stabilization of anatase phase at high temperatures. The obtained experimental results show that cerium doped titania samples stabilizes the anatase phase until 800 °C, whereas copper doped samples calcinated at the same temperature are a mixture of anatase and rutile phases. So, CeO₂ is a better stabilizer for anatase phase than CuO. On the other hand, based on previously reported data it can be concluded that both, CeO₂ and CuO are better stabilizers for anatase phase than SnO₂. It is also verified that the total amount of silica in the titania-silica double oxide increases the temperature required for crystallization, and as a consequence, the anatase phase is stabilized at higher temperatures i.e. up to 1200 °C.     

TiO_2纳米管阵列的制备及其光催化性能研究

采用阳极氧化法在钛箔上制备了TiO_2纳米管阵列,利用场发射扫描电子显微镜(FSEM)、X射线衍射仪(XRD)和紫外-可见分光光度计对TiO_2纳米管的形貌、结构和光学性能进行表征,详细考察了阳极氧化工艺参数对纳米管阵列形貌的影响,探讨了氧化钛纳米管阵列的形成机理,并对其光催化活性进行了测试,研究结果表明:在0.5 wt; HF和1 mol/L H3PO_4电解液中,控制氧化电压为20 V,反应60 min后,在钛箔表面可获得垂直导向的TiO_2纳米管阵列,管内径为60~80 nm,管壁厚约10 nm;600 ℃热处理后的TiO_2纳米管阵列薄膜对349.7 nm近紫外光和443.9 nm可见光有较强的吸收能力;煅烧温度对纳米管的晶型结构和光催化活性有显著影响.     

A facile approach for synthesis of BiVO4 nano‐particles possessing high surface area and various morphologies

BiVO₄ with dominant monoclinic structure and relatively high surface area has been prepared by a simple precipitation method. Smaller particle size and new morphologies were observed while using non‐toxic and common organic additives including ethylene diamine tetra acetic acid (EDTA) as the synthesis constituents. The prepared materials were characterized using structural, textural and microscopic techniques. The photocatalytic activities of the samples were checked using methylene blue, phenol and 2,4,6‐trichlorophenol as probe molecules and visible light as irradiation source. Also, hydrothermally‐ synthesized counterparts of the catalysts were prepared and their structure and photocatalytic efficiency were compared. The recovery of the catalysts after successive uses was also examined.     

Electrospinning synthesis and photocatalytic property of CaFe2O4/MgFe2O4 heterostructure for degradation of tetracycline

CaFe₂O₄/MgFe₂O₄ nanowires with heterostructure had been successfully synthesized by electrospinning method. The obtained samples were systematically characterized by scanning electron microscopy (SEM), X‐Ray diffraction (XRD), UV–Vis diffuse reflectance spectra (UV‐Vis DR) and Environment scanning electron microscopy (ESEM). The novel CaFe₂O₄/MgFe₂O₄ nanowires exhibit an enhanced photocatalytic activity for degrading of tetracycline (TC) under visible light. Compared with bare CaFe₂O₄ or MgFe₂O₄ samples, the prepared CaFe₂O₄/MgFe₂O₄ (Ca:Mg:Fe = 3:2:10) composited nanowires show the best photocatalytic performance with a degradation efficiency of 40% after 150 min reaction time. This enhancement is attributed to the heterostructure of CaFe₂O₄/MgFe₂O₄ nanowires, which effectively repress the recombination of photo‐generated electrons and holes. Based on heterostructure and energy band positions, the enhancement of mechanism under visible‐light enhances the photocatalytic activity.     

g-C3N4和CuO复合材料的制备、表征及光催化研究

高温煅烧三聚氰胺制备类石墨结构氮化碳(g-C3N4),然后以硝酸铜Cu(NO3)2和g-C3N4为原料,去离子水和无水乙醇作溶剂,在加入适量氨水的反应条件下通过水热法反应制备g-C3N4/CuO纳米复合材料.采用场发射扫描电子显微镜(FE-SEM)、光电子能谱仪(XPS)、紫外可见漫反射(UV-Vis-DRS)和荧光光谱(PL)等测试对复合材料进行表征.通过XRD、SEM和XPS测试结果可知微米球形CuO和g-C3N4紧密的结合起来,而由UV和PL谱图表明CuO和g-C3N4的复合扩展了材料对可见光的吸收范围和减慢了材料的光生电子和空穴的复合率.通过在可见光下降解甲基橙(MO)来检测复合材料的光催化活性,结果表明,在没有过氧化氢(H2O2)的体系下,经过4 h的光反应后,70-g-C3N4/CuO对MO的降解率达到了85;;但是在H2O2的体系下,经过1 h光反应后,70-g-C3N4/CuO对MO的降解率达到了96;.通过自由基的捕获实验说明羟基自由基、超氧自由基、空穴在降解MO过程中起到重要的作用.复合材料在经过四次的循环实验后,对MO的降解率基本能达到90;.因此,g-C3N4和CuO的复合抑制了电子-空穴的复合和扩展了吸收光波长范围,这样就使g-C3N4/CuO材料有了好的光催化性和稳定性.     

Ag2O/TiO2异质结的光催化活性及耐光腐蚀性研究

以钛酸丁酯、硝酸铋和硝酸银为原料,FTO为基底,采用水热法结合超声沉积法合成了Ag2 O/TiO2异质结光催化剂.采用场发射扫描电子显微镜(FESEM)、X射线衍射仪(XRD)、紫外-可见吸收光谱(UV-Vis)分析测试手段对样品的形貌和结构进行了表征.结果表明,Ag2O/TiO2异质结是由直径约200 ～ 300 nm的TiO2纳米棒镶嵌着Ag2O纳米颗粒组成,与TiO2纳米棒阵列相比,Ag2O/TiO2异质结在可见光区有明显的光吸收.Ag2O/TiO2异质结的光催化效率明显提高.尤为重要的是,经光处理后,最终得到稳定的Ag-Ag2O/TiO2三元体系,并对Ag-Ag2 O/TiO2三元体系提高光催化稳定性和活性的机理进行了分析.     

Additive‐free solvothermal synthesis of peanut‐like BiVO4 powders with enhanced photocatalysis activity

Monoclinic peanut‐like BiVO₄ products have been successfully synthesized by a solvothermal method. The volume of CH₃COOH and the concentration of NH₃·H₂O were found to play important roles in the formation of this morphology. The optimal condition for preparation of highly active peanut‐like BiVO₄ samples are the volume of CH₃COOH, which was 5 ml, and the concentration of NH₃·H₂O, which was 2 mol/L. The as‐prepared samples were characterized by XRD, SEM, TEM, DRS, BET, and their photocatalytic activity was evaluated by photocatalytic decolorization of a Rhodamine B (RhB) aqueous solution under visible‐light irradiation. The results demonstrated that BiVO₄ with peanut‐like morphology was better than that of other BiVO₄ samples for photodegradation of RhB.     

Anatase phase formation kinetics in Ti and TiOx nanoparticles produced by gas-phase condensation

Anatase TiO₂ nanoparticles were successfully synthesized by post-heat treatments of partially crystalline Ti and amorphous TiO_x nanoparticles, respectively produced by inert gas condensation and subsequent oxidation. The nanoparticles condensed on a liquid-nitrogen containing cooling finger (sample LN) were identified to be partially crystalline Ti phase with ~ 10–20 vol.% amorphous TiO_x. On the other hand, those condensed on a room-temperature cooling finger (sample RT) were almost completely amorphous TiO_x phase. Differential scanning calorimetry scan curves of as-oxidized samples were interpreted using Kissinger analysis, the non-isothermal kinetics, and activation energy for the anatase formation was determined as ~ 455 and 865 kJ/mol for samples LN and RT, respectively. As-oxidized samples LN and RT were heat treated at 400 °C for 2 h, respectively (samples LN-H and RT-H). Samples LN-H and RT-H showed the onset of UV–visible light absorption near 400 nm and the optical band gap of 3.12 and 3.21 eV, respectively, corresponding to anatase. The sample LN-H showed faster photocatalytic decomposition of methylene blue and rhodamine B dyes compared to the sample RT-H due to high crystallinity of anatase and rutile phases.     

Luminescence of polymorph crystalline and glassy SiO2, GeO2: A short review

Studies of SiO₂ and GeO₂ crystals with α-quartz and rutile structures were performed during last two decades. The goal of such studies was comparison of properties with those of glassy modifications of these crystals. Luminescence of oxygen deficient centers in these glassy materials was found to resemble the luminescence of the rutile-type modification rather than α-quartz modification. In α-quartz, similar luminescence centers appear after damaging irradiation by electron beam at low temperatures (<60 K) or at ambient temperatures after gamma or neutron irradiation.     

Formation of quasi-ordered structures on the surface of strontium titanate in a plasma field

The X-ray diffraction and X-ray spectroscopic properties of strontium titanate single crystals and their surface exposed to plasma have been investigated. Both undoped SrTiO₃ crystals and crystals containing impurity ions of the iron or lanthanum groups have been analyzed. Data on the plasma-induced formation of ordered crystallites on the sample surface were obtained by electron and atomic force microscopy. The crystallites are from 10^?7 to 10^?9 m in size and their hypothetical orientation [321] is independent of the sample orientation and irradiation dose.     

Synthesis and characterization of carbon‐doped ZnSn(OH)6 with enhanced photoactivity by hydrothermal method

Well‐dispersed carbon‐doped ZnSn(OH)₆ submicrocubes were successfully synthesized through a facile and economical hydrothermal method at 433K, which used green chemical glucose (C₆H₁₂O₆) as the carbon‐doping source. Photocatalytic activity of the as‐synthesized C‐doped ZnSn(OH)₆ was evaluated by studying photocatalytic decomposition of methylene blue (MB) in aqueous solution under visible light irradiation(≥ 400 nm). The results show that carbon‐doped ZnSn(OH)₆ photocatalysts exhibited higher photocatalytic performance as compared to pure ZnSn(OH)₆. 1.0 wt% C‐doped ZnSn(OH)₆ photocatalyst exhibited obviously higher photocatalytic activity that of pure ZnSn(OH)₆ or other C‐ZnSn(OH)₆ catalysts under the same condition. The enhanced photocatalytic degradation of MB could be attributed to the doping of carbon and the possible mechanism for high photocatalytic activity of C‐doped ZnSn(OH)₆ was discussed.