掺铋纳米TiO_2制备及可见光催化降解有机污染物

采用在酸性条件下超声沉淀的方法低温制备了Bi掺杂TiO_2纳米粉体,采用X射线光电子能谱(XPS)、X射线衍射(XRD)和透射电镜(TEM)对催化剂进行了初步表征,发现其禁带宽度变窄,主要为锐钛矿(82.7%)和金红石(17.3%)混晶,纳米尺寸为25.8nm。以酸性桃红(SRB)和无色小分子2,4-二氯苯酚(2,4-dichlorophenol,2,4-DCP)作为探针反应,在可见光照射下(λ420nm)测定了SRB降解过程中总有机碳(1OC)的变化,发现SRB的TOC去除率为61.6%。跟踪测定光催化反应体系中氧化物种,表明光催化涉及羟基自由基(·OH)过程,所制备的催化剂在可见光下具有较高的催化氧化活性。     

上转光剂掺杂新型纳米TiO2催化剂的制备及利用可见光降解结晶紫染料的研究

合成了一种新型含有稀土金属Er的上转光剂,此上转光剂在488nm可见光的激发下,产生了5个波长均小于387nm的上转换紫外发射峰。采用超声波分散的方法制备出了上转光剂掺杂纳米TiO2可见光光催化剂。以结晶紫为研究对象,研究了光催化剂在可见光(三基色灯下发出)照射下的催化降解性能,并与未掺杂的纳米TiO2粉末的催化性能进行了对比。实验结果表明作为掺杂成分的上转光剂可有效地将可见光转化为紫外光并被纳米TiO2粉末吸收利用,其中380nm转光效率为0.78%。紫外光谱和离子色谱表明,在可见光照射8.0h后降解率达95%以上,高于未掺杂纳米TiO2的48%,结晶紫降解后生成的Cl-和NO3-作为一种无机离子进入溶液中。所有结果表明,掺入上转光剂的TiO2光催化剂是一种有效利用可见光的催化剂,为未来利用太阳光处理工业废水开辟了道路。     

可见光响应负载型Er3+∶YAlO3/TiO2-SAC光催化剂的制备及其性能研究

为使TiO2能在可见光下发挥其于紫外激发的高光催化活性,且易于从处理废水中分离,采用溶胶-凝胶法将TiO2与掺杂稀土离子Er3+的上转换发光剂Er3+∶YAlO3结合再负载到球形活性炭(SAC)表面,制备可见光响应的负载型Er3+∶YAlO3/TiO2-SAC光催化剂并对其进行表征。以甲基橙为目标污染物,研究了制备的催化剂在可见光下催化活性,并探讨不同Er3+∶YAlO3/TiO2的负载方式、负载量等制备条件对光催化剂活性的影响。结果表明,结合方式为Er3+∶YAlO3/TiO2烧结后与SAC在乙醇介质中混合并进行30min磁力搅拌、以Er3+∶YAlO3/TiO2与SAC质量比为1∶4时制备的光催化剂活性最高,甲基橙的脱色率在240min可达97%以上。     

纳米RE/TiO2的制备、表征及光催化还原CO2研究

用溶胶-凝胶法分别制备了掺杂La、Nd和Y三种稀土元素(RE)的纳米TiO2,并用X射线衍射(XRD)、高分辨透射电镜(HR-TEM)和X射线光电子能谱(XPS)等技术表征RE/TiO2催化材料的结构和形貌。研究不同稀土元素及其不同的掺杂量对CO2还原产物甲醛生成量的影响。结果表明,0.1wt%La/TiO2材料的光催化还原CO2性能最佳,在300W高压汞灯(主波长为365nm)照射下,光催化反应6h时甲醛的生成量最大,可达753.21μmol/(g.cat)。     

红磷-TiO_2复合光催化剂的制备及其光催化产氢性能

采用机械混合法制备了红磷-Ti O_2(P-Ti O_2)复合光催化剂,并对催化剂进行了X射线衍射、紫外-可见光漫反射、透射电子显微镜表征。以甲醇为牺牲试剂,铂为助催化剂,在可见光辐照下对P-Ti O_2复合光催化剂进行了光催化分解水产氢性能测试,并提出了红磷和Ti O_2可能的作用机理。研究结果表明:红磷和Ti O_2复合后,光催化剂的产氢性能显著提高,当P-Ti O_2中Ti O_2的质量分数为5%时,光催化剂的产氢性能最高,产氢速率可达到52.6μmol/(h·g),为纯红磷样品的2.54倍;红磷和Ti O_2复合后在其接触面上形成了p-n结,并通过p-n结实现了光生电子从红磷到Ti O_2的传递,从而与Pt发生还原反应产生氢气。     

可见光激发高光催化活性的纳米Ti02光催化剂--丙酮溶剂水热合成、特性表征与光催化活性起因

通过XRD、TEM、TG-DTA和漫反射谱(DRS)等手段,分析了采用丙酮溶剂水热法合成的在可见光波段对甲基橙具有高光催化降解率的纳米TiO2粉体的材料特性与光催化活性的起因.结果表明,经不同温度热处理得到的样品均为锐钛矿晶型、粒径基本相同,但在表面剩余吸附物含量以及可见光波段的光吸收率等方面差异明显,且样品表面剩余吸附物含量、可见光波段的光吸收率与其可见光催化活性之间存在直接关联.分析认为,TiO2表面剩余吸附有机物导致的对可见光的强烈吸收是其可见光波段高光催化活性的重要起因.     

溶胶凝胶法制备氮掺杂二氧化钛及其可见光活性的研究

室温下采用溶胶凝胶法,以氨水为氮源制备出淡黄色氮掺杂二氧化钛粉末。以TG-DSC、XRD、UV-Vis漫反射吸收光谱以及XPS等手段对二氧化钛进行了表征。结果显示,所制备氮掺杂二氧化钛均为锐钛矿相,且掺杂引起光催化剂在可见光区的光吸收。以甲基橙水溶液在紫外及可见光下的脱色率为光催化活性评价依据,结果显示纯二氧化钛无可见光活性,而氮掺杂二氧化钛360 min的最大脱色率可达65.3%,说明氮掺杂有效改变了二氧化钛的可见光活性,但其紫外活性逊于纯二氧化钛。另外,在实验范围内所做的N/Ti配比与光活性的关系研究中发现,可见光活性随N/Ti配比的增大有一最佳值,而紫外光活性顺序与可见光活性不同。     

二次微波法制备纳米TiO_2的实验研究

使用二次微波辅助水热合成法,回避高温煅烧过程,在低温(473K)以下成功制备了锐钛矿型纳米晶体光催化剂TiO_2,样品表征结果证明该粉体样品粒径均匀,晶相单一,具有较大的比表面积和很高的光催化活性。     

载体SiO_2上纳米TiO_2膜的制备及光催化性能

以SiO2 为载体 ,在酸性条件下 ,用TiCl4 水解法制备了TiO2 纳米膜催化剂TiO2 /SiO2 。以IR、XRD、SEM和吸光光度法对其进行了表征 ,所制TiO2 膜的平均粒径在 12nm以内 ,并能在很宽的煅烧温度范围内保持锐钛矿晶体结构 ;将TiO2 /SiO2 应用于光催化降解敌敌畏 (DDVP) ,具有高的光催化活性 ,且易回收及反复使用。探讨了不同条件对光催化活性的影响。     

TiO2-xNx光催化剂的制备及其活性研究

在sol-gel法制备TiO2的过程中引入氨水进行水解,制备了具有可见光活性的TiO2-xNx催化剂,采用UV-Vis、BET、XPS等手段进行表征,以苯甲酸为模型污染物,氙灯为模拟太阳光源,评估了催化可见光催化活性.结果表明,随着焙烧温度的升高,TiO2-xNx的吸光特性增加,当温度超过350%后TiO2-xNx中的氮会在高温下被氧化掉,其吸光特性又降低;此时TiO2-xNx的吸收阈值为422nm,对应的禁带宽度为2.9eV;孔径分布在2.5～8.2nm之间,BET比表面积为139.3m2/g;经计算其x=0.0282,即TiO2-xNx可表示为Ti1.9718N0.0282;在入射波长分别为500nm和600nm时,TiO2-xNx对苯甲酸的去除率分别为6.5%和4.6%,相应的矿化率为3.2%和2.5%.     

Photocatalytic performance of S doped TiO2 in relation to processing conditions: calcination temperature and heating rate

Abstract

The effect of different heating profiles on the photocatalytic performance of sulphur doped TiO₂ photocatalysts is reported. The photocatalysts were synthesised by a sol–gel method using thiourea as the dopant precursor and characterised using X-ray diffraction, elemental analysis and reflection measurements. The degradation of dichloroacetic acid, under indirect sunlight and visible light irradiation, was used to determine the photocatalytic performance of the synthesised materials. A number of different commercial photocatalysts were used as comparative standards. In all the studied specimens, anatase TiO₂ was the dominant crystalline type. Additionally, compared with undoped TiO₂ and commercial standards, significant absorption into the visible region (400–470 nm) was observed for the modified TiO₂.     

Visible light-driven photothermal Au/Ag/TiO2 trihybrid plasmonic nanomaterial for synthetic fuel production

In the present article, a new numerical investigation is conducted to quantify the fluidic flow-photothermal performance of a trihybrid nano-catalyst for biomethane reforming inside a 1 μm micro-reactor on gold-silver nanoparticles coated on titanium oxide (TiO₂). The model generates a two-way coupling between heat, mass, fluid flow and electromagnetic profiles to simulate the plasmonic effect for the plasmonic photocatalyst in a micro-boundary layer adjacent to the catalyst. The effect of light wavelength on operating parameters and system performance was investigated and discussed. This included chemical conversion, the lower heating value of the syngas, mole fractions of species in the gaseous product, and the spatiotemporal velocity profiles. It was found that light absorptance by the nanoparticles is highest when visible light wavelength within 570 nm < λ < 590 nm is used to stimulate the plasmonic nanostructure. Also, the chemical conversion reached 81% at an exposure time of 1 μs of visible light. At λ = 570 nm, the produced syngas had a lower heating value of 311 kJ/mol and syngas quality of 0.16, which is suitable for ethanol production. Also, a maximum temperature elevation of 998 K was achieved which is above the minimum temperature required for reforming methane (823 K). The spatiotemporal velocity and chemical conversion profiles across the micro-reactor showed that at exposure times > 5 μs, both profiles become fully developed resulting in the suppression of chemical conversion.     

TiO2纳米管限域Fe2O3的可见光分解水制氢性能

通过真空−超声辅助的等体积浸渍法制备了TiO2纳米管限域Fe2O3催化剂,考察了其可见光分解水制氢性能。由于TiO2纳米管的限域效应,导致Fe2O3颗粒减小,分散度提高,能隙增大,光生载流子得到有效分离,提高了其光解水制氢活性。     

Ce掺杂TiO2光催化剂的制备及降解偶氮废水的研究

采用溶胶—凝胶法制备Ce掺杂TiO2光催化剂,借助XRD、HRTEM对其进行表征,分析了Ce含量、煅烧温度等因素对光催化降解偶氮废水活性的影响。结果表明,铈掺杂在提高了TiO2光催化剂催化活性的同时也抑制了相转变。当Ce的掺杂量为3%时,对偶氮废水的处理率可高达92.3%。     

Preparations and photocatalytic hydrogen evolution of N-doped TiO2 from urea and titanium tetrachloride

Nitrogen (N)-doped TiO₂ samples with high specific surface areas were directly prepared by heating the mixture of urea and TiO₂, where the TiO₂ was obtained with titanium tetrachloride as precursor. The absorption spectrum of the N-doped TiO₂ shifted to wavelength up to 600 nm with increasing urea contents. X-ray photoelectron spectroscopic measurements showed that the N presented in TiO₂ was in the state of both molecularly chemisorbed N₂ and substituted N. While both of them contribute to the response to visible light, the latter gave the prepared samples with hydrogen evolution under visible light. The apparent photocatalytic activity of water splitting demonstrated as high amount of H₂ evolution was partly due to the phase transformation from anatase to rutile for the N-doped TiO₂.     

Enhancing hydrogen evolution of water splitting under solar spectra using Au/TiO2 heterojunction photocatalysts

An effective improvement of hydrogen evolution from water splitting under solar light irradiation was investigated using quantum dots (QDs) compounds loaded onto a Au/TiO₂ photocatalyst. First, Au/TiO₂ was prepared by the deposition-precipitation method, and then sulfide QDs were loaded onto the as-prepared Au/TiO₂ by a hydrothermal method. QDs were loaded onto Au/TiO₂ to enhance the energy capture of visible light and near-infrared light of the solar spectrum. The results indicated that the as-prepared heterojunction photocatalysts absorbed the energy from the range of ultraviolet light to the near-infrared light region and effectively reduced the electron-hole pair recombination during the photocatalytic reaction. Using a hydrothermal temperature of 120 °C, the as-prepared (ZnS–PbS)/Au/TiO₂ photocatalyst had a PbS QDs particle size of 5 nm, exhibited an energy gap of 0.92 eV, and demonstrated the best hydrogen production rate. Additionally, after adding 20 wt % methanol as a sacrificial reagent to photocatalyze for 5 h, the hydrogen production rate reached 5011 μmol g⁻¹ h⁻¹.     

Electrophoretic Deposition of TiO2/Nb2O5 Composite Electrode Thin Films for Photovoltaic Application

Nano sized powders of TiO2 （titanium dioxide） and Nb2O5 （Niobium （V） oxide） were used to fabricate TiO2/Nb2O5 composites thin films by EPD （electrophoretic deposition） technique. The metal oxide powders, together with magnesium nitrate hexahydrate pellets, were suspended in propan-2-ol inside an EPD cell. The electrodes, placed 1.2 cm apart, were partially immersed in the suspension and a DC potential applied across them. Key EPD process parameters, which include applied DC electric field, deposition time and solid concentration in suspension, were optimized through visual inspection and from UV-Vis-NIR spectrophotometer spectra. The highest （55%） transmittance was obtained for films with deposition time of 90 s, powder concentration of 0.01 g/40 mL, and 35 V DC （direct current） voltage. XRD micrographs confirmed that TiO2 and Nb2O5 particles were presented in the composite film. SEM （scanning electron microscope） micrographs of the composite electrode thin films showed that porous films of high quality with well controlled morphology were deposited by using the EPD technique.     

Photocatalytic activity of TiO2 nanotube layers coated with Ag and Pt

Abstract

Abstract

Thin films of anatase TiO₂ nanotube arrays (TiO₂ NTs) were prepared in this study. Pt and Ag were coated on the TiO₂ NTs films, which intend to increase the photocatalytic activity under ultraviolet-visible (UV-vis) irradiation. The phase and structure of the films were investigated by X-ray diffraction and scanning electron microscopy. Photocatalytic activity was tested by UV-vis absorption spectroscopy and showed that UV-vis light absorption of the films was remarkably improved by coated Ag and Pt by 72% and 183% respectively. The photocatalytic activities of the films towards degraded methyl orange and HCHO were compared and were all found to follow the sequence Pt/TiO₂ NTs>Ag/TiO₂ NTs>TiO₂ NTs. It was also found that the kinetics of HCHO photocatalytic degradation by the films fits the first order reaction model better and has higher efficiency than that of the methyl orange photocatalytic degradation by the same films.     

Highly efficient photocatalytic conversion of gas phase CO2 by TiO2 nanotube array sensitized with CdS/ZnS quantum dots under visible light

With the massive consumption of fossil fuels, energy crisis and effectively reducing CO₂ to curb global warming have become urgent and severe problems in the world. Photocatalytic conversion of CO₂ technology which can convert CO₂ into combustible compounds by using solar energy can solve both of the problems mentioned above. However, the photocatalytic conversion of CO₂ exhibits too low efficiency, especially under visible light. So, in order to improve the photocatalytic efficiency, the composite photocatalysts of TiO₂ nanotube array (TNTA) sensitized by CdS/ZnS quantum dots (QDs) were successfully prepared by anodization method and successive ionic layer adsorption and reaction (SILAR) method in this work. And the composite photocatalysts exhibited a high performance for photocatalytic conversion of gas-phase CO₂ to methanol under visible light. X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), and X-ray photoelectric spectroscopy (XPS) were employed to characterize the ingredients and morphologies of the synthesized photocatalysts. And, UV–vis diffuse reflectance spectra (UV–Vis DRS) revealed that CdS/ZnS QDs enhanced the photo-absorption of composite photocatalyst in the visible light region. The main product methanol yield of CdS/ZnS-TNTA under visible light was 2.73 times that of bare TNTA when TNTA was treated by 10 SILAR cycles. Meanwhile, the product yield first increased before decreasing with the increase of the CO₂ flow rate. And the greatest product yield reached up to 255.49 nmol/(cm²-cat·h) with the increase of light intensity. The reaction mechanism was discussed in this paper. This high performance for photocatalytic reduction of CO₂ was primarily attributed to the CdS/ZnS QDs sensitization, which widens the response wavelength range of the catalyst to include visible light and partly inhibits the recombination of electron-hole pairs.     

Electronic structure and photocatalytic properties of copper-doped CaTiO3

Perovskite oxides, CaTi_1−xCu_xO₃, with the density of copper ions, x, ranging from 0.01 to 0.04, were prepared by sol-gel method coupled with ultrasonic technique for the first time. The determination by X-ray diffraction pattern of crystal structure and UV–visible light adsorption studied by ultraviolet-visible absorption spectroscopy (UV–vis) were reported. Electronic structures were investigated by density functional theory (DFT). It has been found that CaTiO₃-doped with 2 mol% Cu²⁺ exhibits the highest activity to the photocatalytic decomposition of water. Photocatalytic activity of doped CaTiO₃ powder for hydrogen evolution under UV light is increased dramatically about 8 times than that of pure CaTiO₃ powder when the NiO_x is used for cocatalyst. The results of DFT calculation illuminate that absorption of visible light is mainly due to the transition from the donor levels formed by Cu²⁺ to the conduction band of copper-doped CaTiO₃.