Synthesis and photocatalytic activity of mesoporous cerium doped TiO2 as visible light sensitive photocatalyst

Cerium doped titania materials were synthesized varying the cerium concentration from 0 to 10 wt%. Materials are characterised by XRD, TEM, XPS and N₂ adsorption desorption method. Surface area and visible light absorption substantially increases and crystallite size decreases with the increasing cerium content. Cerium doping stabilizes the anatase phase and surface area even at 600 °C calcination. Photocatalytic activity towards methylene blue decomposition and selenium (IV) reduction is found to increase with the cerium content up to 5 wt% and then decreases. Materials calcined at 600 °C shows better activity than that calcined at 400 °C, even though surface area decreases. Anatase crystallinity mostly decides the photocatalytic activity rather than only surface area. It can be concluded that the optimum visible light absorption and oxygen vacancy with 5% cerium doping enhances the photocatalytic activity. In addition photocatalytic performance is found to depend on the presence of Ce⁴⁺/Ce³⁺ rather than only visible light absorption.     

Fabrication and enhanced visible light photocatalytic activity of fluorine doped TiO2 by loaded with Ag

F-doped TiO2 loaded with Ag (Ag/F-TiO2) was prepared by sol-gel process combined with photoreduction method. The physical and chemical properties of the prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL). XPS analysis indicated Ag species existed as Ag0 in the structure of Ag/F-TiO2 samples. UV-Vis diffuse reflectance spectra showed that the light absorption of Ag/F-TiO2 in the visible region had a significant enhancement compared with the F-doped TiO2 (F-TiO2). PL analysis indicated that the electron-hole recombination rate had been effectively inhibited when Ag loaded on the surface of F-TiO2. The photocatalytic activities of the samples were evaluated for the degradation of X-3B (Reactive Brilliant Red dye, C.I. reactive red 2) under visible light (lambda > 420 nm) irradiation. Compared with F-TiO2, the sample of 0.50 Ag/F-TiO2 showed the highest photocatalytic activity. The interaction between F species and metallic Ag was responsible for improving the visible light photocatalytic activity.     

Photocatalyzed degradation of flumequine by doped TiO2 and simulated solar light

Titanium dioxide was obtained in its pure form (TiO₂) and in the presence of urea (u-TiO₂) and thiourea (t-TiO₂) using the sol–gel technique. The obtained powders were characterized by BET surface area analysis, Infrared Spectroscopy, Diffuse Reflectance Spectroscopy and the Rietveld refinement of XRD measurements. All the prepared catalysts show high anatase content (>99%). The a and b-cell parameters of anatase increase in the order TiO₂ < u-TiO₂ < t-TiO₂, while the c-parameter presents the opposite trend. Because of the interplay in cell dimensions, the cell grows thicker and shorter when prepared in the presence of urea and thiourea, respectively. The cell volume decreases in the order t-TiO₂ > u-TiO₂ > TiO₂. The photocatalytic activities of the samples were determined on flumequine under solar-simulated irradiation. The most active catalysts were u-TiO₂ and t-TiO₂, reaching values over 90% of flumequine degradation after 15 min irradiation, compared with values of 55% for the pure TiO₂ catalyst. Changing simultaneously the catalyst amount (t-TiO₂) and pH, multivariate analysis using the response surface methodology was used to determine the roughly optimal conditions for flumequine degradation. The optimized conditions found were pH below 7 and a catalyst amount of 1.6 g L⁻¹.     

非金属元素掺杂TiO2可见光催化原理的探讨

本文从几篇文献的误解入手,介绍了掺氮二氧化钛(TiO2)具有可见光活性的几种不同观点,在分析后,得出掺氮TiO2具有可见光活性是由于两方面的因素造成的:一是氮的掺杂使TiO2的价带产生变化,这种变化使价带附近的空穴活动性降低、带隙变小;二是掺氮TiO2存在氧空位,并且氧空位在导带边缘,使能带变窄.同时还介绍了掺硫TiO2、掺碳TiO2吸收可见光的原理.     

铁掺杂TiO2光催化剂的制备及光催化性能

采用溶胶-凝胶法制备铁掺杂纳米TiO2光催化剂。通过XRD、FT-IR、UV-Vis、PL等对Fe-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铁量Fe-TiO2样品对MB的降解效果。结果表明所制备的Fe-TiO2样品的晶型为锐钛矿相与金红石相的混晶相,铁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68nm,提高了TiO2的光催化活性。在普通日光灯下,经500℃热处理、掺铁量与TiO2摩尔比为1∶200条件下制备的催化剂其光催化活性明显高于Degussa P25。     

Fabrication and characterization of FePt magnetic nanofibers via electrospinning technique

L1₀-structured platinum–iron (FePt) nanofibers were successfully synthesized by electrospinning technique, followed by calcination and reduction processes. In the preparation procedure, ferrous chloride tetrahydrate [Fe(Cl)₂?4H₂O] and iron nitrate nonahydrate [Fe(NO₃)₃?9H₂O] were, respectively, used as iron sources contained in precursor solution for electrospinning. Subsequently, the FePt nanofibers were obtained from the calcination in air and the followed reduction in hydrogen (H₂) of the as-spun FePt/PVP composite nanofibers. The FePt nanofibers were characterized by X-ray diffractometer, scanning electron microscopy, transmission electron microscopy, and superconducting quantum interference device magnetometry. It was found that the different iron salt used in the spinning solutions could highly affect the FePt nanofiber morphology, crystallite size, and the magnetic properties. The FePt nanofibers, resulted from the spinning solution containing iron dichloride tetrahydrate, were of better crystallinity and well-defined fibrous morphology with an average diameter of about 110 nm. Additionally, the considerably large coercivity of 10.27 kOe was recorded from the above FePt nanofibers.     

静电纺丝制备Fe2O3-TiO2纳米纤维及光催化性能研究

采用静电纺丝法制备了Fe2O3掺杂纳米TiO2的有机无机PVP/Fe2O3-TiO2纤维,经高温焙烧得到Fe2O3-TiO2纳米纤维。利用差动-热重(DSC-TGA)、傅里叶红外光谱(FT-IR)、扫描电镜(SEM)、XRD和比表面积分析仪等对样品进行了表征。以10mg/L亚甲基蓝溶液为底物,研究了Fe2O3掺杂量和焙烧温度等对亚甲基蓝太阳光催化降解效果的影响。结果表明,掺杂量为0.08%、焙烧温度为500℃得到的Fe2O3-TiO2纳米纤维光降解效果最好,达到96.3%,重复使用7次降解率仍在90%以上。     

Adsorption and solar light activity of transition-metal doped TiO<Subscript>2</Subscript> nanoparticles as semiconductor photocatalyst

There is an eminent interest to improve the photoactivity of TiO₂ nanostructures via doping with mid-band gap donors or acceptors to achieve a high solar absorption. In the present work, Cr- and V-doped TiO₂ nanoparticles were prepared via a facile chemical vapor synthesis method. The effect of the transition metals (TM) on the solar light activity of the semiconductor nanoparticles as photocatalyst was examined by degradation of methylene blue and acid red 27. Induced coupled plasma and X-ray photoelectron spectroscopy analyses indicated high efficiency of the doping process in the hot wall reactor without surface covering of the TiO₂ nanoparticles by the dopants. Diffuse reflectance spectroscopy also revealed a red shift of the absorption edge of the TiO₂ nanoparticles with increasing dopant concentration. Analysis of the photoactivity of the synthesized nanoparticles under sun light showed an increase in the primary absorption of dye molecules on the surface of Cr- and V-doped TiO₂ nanoparticles whereas the degradation rate was found to depend on the type and concentration of the dopants. A high photoactivity is obtained at 0.2 at% V concentration. The mechanism of photoactivity is discussed based on the effect of TM on the absorption edge of the semiconductor.     

Fabrication of the CN co-doped rod-like TiO2 photocatalyst with visible-light responsive photocatalytic activity

The CN co-doped TiO₂ nanorods were synthesized by the vapor transport method of water molecules, and urea was used as the carbon and nitrogen source. The samples were characterized by X-ray diffraction and photoelectron spectroscopy analysis. The scanning electron microscope images showed that as-prepared TiO₂ powders were nanorods, which were formed by the stacking of nanoparticles with a uniform size around 40 nm. The degradation of methylene blue with the prepared nanorods demonstrated the photocatalytic activities of TiO₂ under visible light are improved by doping with C and N elements. The main reasons were discussed: doping with C and N elements could enhance the corresponding visible-light absorption of TiO₂. On the other hand, doping C and N could create more oxygen vacancies in the TiO₂ crystals, which could capture the photogenerated electrons more effectively. Thus, more photogenerated holes could be left to improve the photocatalytic activity of TiO₂.     

具有可见光活性的纳米掺氮TiO2制备和表征

用硫酸钛与氨水反应得到TiO2前体,煅烧后制得掺氮TiO2粉体,研究不同反应条件和不同温度下掺氮TiO2的吸光特性和形态结构,结果表明掺氮TiO2在400℃：下加热1h,所得粉体是锐钛矿相结构,粒径约15nm,与未掺杂TiO2相比,吸收边红移22nm,对400-510nm的可见光有一定的吸收率,可见光下对甲基橙的降解表明具有可见光活性。     

铁掺杂TiO2光催化性能研究进展

介绍了铁离子掺杂TiO2光催化剂改性的机理,基于密度泛函理论的平面波超软赝势方法验证了铁掺杂TiO2光催化改性机理.介绍了铁离子单掺杂和共掺杂TiO2光催化技术的研究进展,并对未来光催化技术研究方向进行了展望.     

Fabrication and characterization of electrospun Ag doped TiO2 nanofibers for photocatalytic reaction

Titanium dioxide is one of the best semiconductor photocatalysts available for photocatalytic reaction of dye pollutants. To prevent the recombination caused by the relatively low photocatalytic efficiency, Ag doped TiO₂ nanofiber was prepared by electrospinning method. The photocatalysts (pure TiO₂ nanofiber and Ag doped TiO₂ nanofiber) were characterized by FE-SEM, XRD, XPS, and PL analysis. These photocatalysts were evaluated by the photodecomposition of methylene blue under UV light. Ag doped TiO₂ nanofiber was found to be more efficient than pure TiO₂ fiber for photocatalytic degradation of methylene blue. The photocatalytic degradation rate was applied to pseudo-first-order equation. The degradation of Ag doped TiO₂ nanofiber was significantly higher than the degradation rate of pure TiO₂ nanofiber. Activation energy was calculated by applying Arrhenius equation from the rate constant of photocatalytic reaction. The activation energies for the pure TiO₂ nanofibers calcined at 400 and 500 °C were 16.981 and 12.187 kJ/mol and those of Ag doped TiO₂ nanofibers were 18.317 and 7.977 kJ/mol, respectively.     

Preparation and characterization of N-S-codoped TiO(2) photocatalyst and its photocatalytic activity

N-S-codoped anatase nanosized TiO(2) photocatalyst (NSTO) was successfully prepared by one-step hydrothermal method from a mixed aqueous solution of Ti(SO(4))(2) and thiourea. The samples were characterized by XRD, UV-vis, XPS, FT-IR and EA. From results of UV-vis, a red shift of the absorption edge was brought out owing to N and S codoping, and the extension for photoabsorption range of NSTO occurred. XRD, XPS, EA and FT-IR studies revealed that N and S were in situ codoped in the lattice of TiO(2) and N concentration decreased from the surface to the center of NSTO. Especially, the photocatalytic tests indicated that NSTO exhibited a high activity for decompositions of methyl orange both under UV-light and vis-light irradiation comparing to S-doped TiO(2) (STO) and undoped TiO(2) (TO). The high activity of NSTO can be related to the results of the synergetic effects of strong absorption in the UV-vis region, red shift in adsorption edge, oxygen vacancies and the enhancement of surface acidity induced by N and S codoping.     

TiO2 doped with nitrogen: synthesis and characterization

In this study, nitrogen-doped titanium dioxide (TiO2) powders were synthesized in two ways: by heating of titanium hydroxide with urea and by direct hydrolysis of titanium tetraisopropoxide (TTIP) with ammonium hydroxide. The samples were characterized by structural (XRD), analytical (XPS), optical (UV/Vis absorption/reflection and Raman spectroscopy) and morphological (SEM, TEM) techniques. The characterization suggested that the doped materials have anatase crystalline form without any detectable peaks that correspond to dopants. The absorption threshold of titanium dioxide was moved in the visible range of optical spectrum from 3.2 eV to 2.20 eV. Particle sizes of synthesized powders were obtained from XRD measurements and from TEM data ranging from 6-20 nm. XPS and Raman spectroscopy were used for detection of nitrogen in doped samples.     

Synthesis and characterization of visible light driven mesoporous nano-photocatalyst MoO3/TiO2

A novel mesoporous-structured photocatalyst MoO3/TiO2 was synthesized through a modified sol-gel method by using P123 as the template, and the resulting nano-photocatalysts were characterized by X-ray diffraction (XRD), N2 adsorption measurements, transmission electron microscope (TEM), UV-vis spectroscopy, XPS and Raman techniques. Low-angle XRD and TEM images show the lack of long-range order in the as-prepared MoO3/TiO2, but the Mo species are homogenously dispersed on the anatase matrix. According to the results of N2 ads-desorption, the calcined products possess the high surface area and the pore size distribution centered between 4-7 nm. The calcined meso-MoO3/TiO2 materials exhibit the high photocatalytic activity for the degradation of MB (methylene blue) under visible light radiation.     

碳纤维负载钐掺杂纳米TiO2复合材料的制备与表征

采用静电纺丝法和热处理工艺制备了纳米碳纤维负载掺杂1.5%(摩尔分数)Sm的纳米Ti O2复合材料(Sm-Ti O2/CNFs),利用SEM、EDX、TEM、FTIR和XRD对其组成和结构进行了表征,并以甲基橙为降解对象,考察了Sm-Ti O2/CNFs复合材料在紫外光照射下对甲基橙的光催化降解效果。结果表明,掺杂Sm3+的Ti O2以锐钛矿晶型均匀分散在碳纳米纤维的表面和内部,质量分数为20%左右;相对于未掺杂的Ti O2/CNFs样品,Sm-Ti O2/CNFs的光催化活性提高约37%。     

Facile synthesis of binary metal substituted copper oxide as a solar light driven photocatalyst and antibacterial substitute

This work presents the synthesis of Cu_0.95Mn_0.05O (CMO), Cu_0.95Ag_0.05O (CAO), and Cu_0.9Mn_0.05Ag_0.05O (CMAO) samples via wet chemical route for photocatalytic and antibacterial applications. The phase, morphology, chemical composition, and absorption range of the transition metal substituted CuO samples were investigated using various techniques such as PXRD, FESEM, EDX, and UV/Visible spectroscopy . The photocatalytic and antibacterial aptitude of all the synthesized samples was tested using methylene blue (MB) and bacterial strains. The results of application studies showed that the CMAO sample has a greater potential for dye degradation and bacterial strain destruction because of its long-lived photo-generated reactive species. More precisely, among all the synthesized samples, the CMAO sample showed excellent photocatalytic activity and degraded 83.9% dye at a higher rate constant value (0.0127 min^?1). Moreover, the CMAO sample also showed better bactericidal activity against Gram-positive (S. aureus) and Gram-negative bacterial strains (E. coli). Actually, components of the bacterial cell membrane are also organic like organic dyes, so they are likely to degrade by photo-generated species. The results revealed that binary metal substituted CuO (CMAO) has an excellent ability to kill bacteria and eliminate toxic dyes from industrial effluents.     

Novel solar light driven photocatalyst, zinc indium vanadate for photodegradation of aqueous phenol

In the present investigation, we have demonstrated the synthesis of novel photocatalyst, zinc indium vanadate (ZIV) by solid-solid state route using respective oxides of zinc, indium and vanadium. This novel photocatalyst was characterized using XRD, FESEM, UV-DRS and FTIR in order to investigate its structural, morphological and optical properties. XRD clearly shows the formation of phase pure ZIV of triclinic crystal structure with good crystallinity. FESEM micrographs showed the clustered morphology having particle size between 0.5 and 1 μm. Since, optical study showed the band gap around 2.8 eV, i.e. in visible region, we have performed the photocatalytic activity of phenol degradation under visible light irradiation. The photodecomposition of phenol by ZIV is studied for the first time and an excellent photocatalytic activity was obtained using this novel photocatalyst. Considering the band gap of zinc indium vanadate in visible region, it will also be the potential candidate for water splitting.