微波法制备SO_4~(2-)_/TiO_2催化剂及其光催化氧化性能

采用微波法、混合加热法和常规加热法制备 SO_4~(2-)/TiO_2催化剂 ,运用 XRD、 BET、 DRS及 LRS光谱测定等技术对催化剂的结构进行了表征 ,并以光催化降解 C2H4为模型反应考察了不同制备方法对催化剂的光催化氧化反应性能的影响 .研究结果表明 ,微波法制备的 SO_4~(2-)/TiO_2催化剂的光催化氧化性能得到明显改善 ,对乙烯转化率为 80％ ,而混合加热法和常规加热法制备的样品乙烯转化率分别为 58％和 41％ .微波辐射制备的催化剂锐钛矿相含量高、比表面积大 ,光吸收阈值增大;并且拉曼散射光谱向低波数方向移动 ,有助于增加光致电子的跃迁几率 ,提高多相光催化过程的本征量子效率 .     

微波法制备SO2-4/TiO2催化剂及其光催化氧化性能

采用微波法、混合加热法和常规加热法制备/TiO2催化剂,运用XRD、BET、DRS及LRS光 谱测定等技术对催化剂的结构进行了表征,并以光催化降解C2H4为模型反应考察了不同制备 方法对催化剂的光催化氧化反应性能的影响.研究结果表明,微波法制备的/TiO2催化剂的光 催化氧化性能得到明显改善,对乙烯转化率为80％,而混合加热法和常规加热法制备的样品乙 烯转化率分别为58％和41％.微波辐射制备的催化剂锐钛矿相含量高、比表面积大,光吸收阈 值增大;并且拉曼散射光谱向低波数方向移动,有助于增加光致电子的跃迁几率,提高多相光 催化过程的本征量子效率.     

原位红外光谱法研究La/TiO2对有机污染物的光催化降解

本工作采用改进的溶胶-凝胶法和浸渍法制备了TiO₂掺杂稀土离子La³⁺的La/TiO₂光催化剂，运用XRD、N₂吸附脱附、紫外可见漫反射光谱(DRS)、表面光电压谱(SPS)等手段进行表征，同时利用原位红外技术考察了La/TiO₂样品光催化降解乙烯、丙酮、苯的气-固相光催化氧化反应，对其光催化降解有机污染物的过程进行了研究。结果表明，TiO₂经适量La³⁺掺杂后，锐钛矿晶型的含量增加，晶粒度减小，比表面积增大，禁带宽度增加，表面光电压信号增强，光生电子-空穴对有效分离；La/TiO₂样品对乙烯、丙酮、苯的光催化性能与纯TiO₂相比均有不同程度的改善，乙烯可以被光催化氧化完全矿化生成CO₂，而丙酮被光催化氧化可能生成中间产物丙酸，苯被光催化氧化可能生成中间产物苯酚和苯醌。     

以乙二醇为电子给体在CuO/TiO2上光催化分解水制氢

采用浸渍、热分解的方法在TiO₂纳米颗粒上负载CuO制备得到光催化剂CuO/TiO₂。研究了以乙二醇为电子给体,在CuO/TiO₂上光催化分解水制氢的反应过程。重点分析考察了影响光催化产氢速率的因素如CuO的负载量、反应时间、光催化剂用量、乙二醇初始浓度等,同时对光催化制氢的反应机理进行了初步探讨。结果表明,氙灯光源模拟太阳光下最佳产氢速率达到604.5 μmol·h^-1·g^-1;CuO/TiO₂催化剂改善了光吸收性能、减少了光生载流子的复合速率,CuO可以起到传输电子的作用;乙二醇为电子给体很可能经过羟基乙醛进一步被氧化。     

以乙二醇为电子给体在CuO/TiO2上光催化分解水制氢

采用浸渍、热分解的方法在TiO₂纳米颗粒上负载CuO制备得到光催化剂CuO/TiO₂。研究了以乙二醇为电子给体,在CuO/TiO₂上光催化分解水制氢的反应过程。重点分析考察了影响光催化产氢速率的因素如CuO的负载量、反应时间、光催化剂用量、乙二醇初始浓度等,同时对光催化制氢的反应机理进行了初步探讨。结果表明,氙灯光源模拟太阳光下最佳产氢速率达到604.5μmol·h^-1·g^-1;CuO/TiO₂催化剂改善了光吸收性能、减少了光生载流子的复合速率,CuO可以起到传输电子的作用;乙二醇为电子给体很可能经过羟基乙醛进一步被氧化。     

阳极氧化法制备TiO2纳米管及其光催化性能

纳米TiO₂对诸多环境污染物有显著的光催化降解作用,光催化已发展成为新型环境污染治理技术。本文采用阳极氧化法制备出TiO₂纳米管,对比了四种电解液组成(A氟化铵+硫酸铵+水;B氟化铵+硫酸铵+乙酸+水;C氟化铵+硫酸铵+甘油+水;D氢氟酸+二甲基亚砜(DMOS)+乙醇)对催化剂表面形貌及光催化性能的影响。结果表明,电解液A和C都制备出了形貌清晰的TiO₂纳米管,管径约为60~74 nm。样品经400 ℃煅烧,TiO₂晶型主要为锐钛矿相;经500 ℃煅烧,出现少量金红石相;经700 ℃煅烧,晶型全部为金红石相。具有良好形貌的TiO₂纳米管同时具有良好的紫外光吸收能力。当亚甲基蓝初始浓度为10 mg·L^-1,经500 ℃煅烧的TiO₂纳米管光催化活性最佳,光照30 min亚甲基蓝的降解率达89.98%。亚甲基蓝光催化降解反应符合一级反应动力学,反应速率常数为0.079 30。     

Pt / InVO4 / TiO2可见光催化剂的制备及性能研究

采用溶胶-凝胶法制备了Pt / InVO₄ / TiO₂三元体系可见光催化剂。以乙烯为模拟目标分子，评价其光催化活性并与二元体系催化剂Pt / TiO₂ 和InVO₄ / TiO₂进行比较。用DRS，XRD对催化剂的吸收带边和晶型进行了表征。结果表明：Pt / InVO₄ / TiO₂在可见光区（λ>450 nm）的光催化比活性比Pt / TiO相似文献   

部分还原氧化石墨烯/二氧化钛复合材料的水热合成及其光催化活性

采用水热法以Hummers氧化法制备的氧化石墨和钛酸四丁酯为原料制备了部分还原的氧化石墨烯/二氧化钛(RGO/TiO₂)复合光催化剂, 并研究了该复合材料在可见光以及紫外光下对亚甲基蓝的光催化降解活性.结果表明, 通过改变反应温度和氧化石墨加入量可以调控TiO₂的晶相组成及其在复合材料中的分散性; 在水热反应过程中氧化石墨烯发生了部分还原; 所制备的RGO/TiO₂复合材料的可见光和紫外光催化活性均高于纯TiO₂; 部分还原的氧化石墨烯在复合材料中担当载体和电子受体, 同时可以使TiO₂的初始吸收边向可见光区域红移, 增强了TiO₂在可见光区域的吸收, 能有效提高对目标污染物的吸附性和光催化降解活性.     

铋掺杂二氧化钛纳米颗粒的制备及其可见光催化性能

采用水热法,以纳米管钛酸为前驱物制备了Bi掺杂的TiO₂,并利用X射线衍射、透射电子显微镜、X射线光电子能谱、紫外-可见漫反射光谱等手段对样品进行了表征. 以甲基橙的光催化降解为模型反应评价了样品的可见光催化性能. 结果表明,Bi离子并没有进入TiO₂的晶格中,而是以BiOCl的形式存在. 所制得的BiOCl/TiO₂复合物对甲基橙降解表现出较优越的可见光催化活性;当Bi/Ti摩尔比为1%,水热温度为130℃时,所制催化剂的光催化性能最佳,并对光催化活性提高的机理进行了讨论. 同时,该催化剂对4-氯苯酚降解也表现出较高的光催化性能.     

卟啉锡敏化TiO2纳米管的光催化活性和光电性能

制备了反-二羟基-5,10,15,10-四苯基卟啉锡敏化的TiO₂纳米管,并以对硝基苯酚为模型污染物,对其在可见光照射下的光催化活性进行了研究。同时,将卟啉锡敏化的TiO₂纳米粒子作为参照物,探讨了形貌对催化剂光催化活性的影响。实验结果表明,卟啉锡的引入可以明显地增强TiO₂纳米管的可见光催化活性。与TiO₂纳米粒子相比,卟啉锡对TiO₂纳米管的敏化作用更加显著,表明催化剂的形貌在光催化过程中具有重要作用。此外,我们还考察了卟啉锡敏化的TiO₂纳米管的光电化学行为,并与其光催化活性相关联。最后,对卟啉锡的敏化机理进行了初步的探讨。     

Effect of Cl− anions on photocatalytic decomposition of gaseous ozone over Au @ Ag/TiO2 catalyst

Au core Ag shell composite structure nanoparticles were prepared using a sol method. The Au core Ag shell composite nanoparticles were loaded on TiO₂ nanoparticles as support using a modified powder–sol method, enabling the generation of Au @ Ag/TiO₂ photocatalysts for photocatalytic decomposition and elimination of ozone. The sols were characterized by means of ultraviolet–visible light (UV–Vis) reflection spectrometry, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The activity of the Au @ Ag/TiO₂ photocatalysts for photocatalytic decomposition and elimination of ozone was evaluated and the effect of Cl^? anions on the photocatalytic activity of the catalysts was highlighted. Results showed that Au @ Ag/TiO₂ prepared via the modified powder–sol route in the presence of an appropriate amount of NaCl solid as demulsifier had better activity in the photocatalytic decomposition and elimination of ozone. At the same time, Au @ Ag/TiO₂ catalysts had better ability to resist poisonous Cl^? anions than conventional Au/TiO₂ catalyst. The reasons could be, first, that NaCl was capable of reducing the concentration of free Ag⁺ by adsorption on the surface of Ag particles forming AgCl and enhancing the formation of Au core Ag shell particles, leading to a better resistance to Cl^? anions of the catalysts, and, second, AgCl took part in the photocatalytic decomposition of ozone together with Au @ Ag/TiO₂ catalysts and had a synergistic effect on the latter, resulting in better photocatalytic activity of Au @ Ag/TiO₂ catalysts.     

Environmental remediation by an integrated microwave/UV illumination technique: IX. Peculiar hydrolytic and co-catalytic effects of platinum on the TiO2 photocatalyzed degradation of the 4-chlorophenol toxin in a microwave radiation field

The photocatalyzed degradation of the 4-chlorophenol toxin (4-CP) in aqueous naked TiO₂ and platinized TiO₂ suspensions simultaneously subjected to UV light and microwave radiation was revisited to examine the fate of this toxin in the microwave-assisted photocatalytic process by monitoring loss of total organic carbon (TOC; mineralization), formation of chloride ions (dechlorination of 4-CP), and identification of intermediates using HPLC and electrospray mass spectral (LC–MSD) techniques. Attempts are made to delineate microwave thermal and nonthermal factors that impinge on the degradation by comparing experimental results from microwave-generated heat versus results from a conventional (externally heated) thermally-assisted process, and from results in which the thermal factors were minimized by examining the degradative process at constant ambient temperature (25 °C). Possible microwave radiation effects on the Pt co-catalyst supported on TiO₂ were also probed through comparison of the degradation of 4-CP occurring on Pt/TiO₂ and on naked TiO₂ photocatalysts. Results suggest that, in a microwave radiation field, naked TiO₂ and Pt/TiO₂ particle surfaces interact with the microwaves. The degradation pathway exhibited characteristics of hydrolysis of reactants and intermediates. Nonthermal microwave effects play a role in the overall degradative process occurring in platinized TiO₂ dispersions. The possible nature of these unusual microwave effects is briefly discussed.     

Preparation of TiO2 nano-particle photocatalysts by a multi-gelation method: the effect of pH change

TiO₂ photocatalysts were prepared by a multi-gelation method and the effect of the changes in the pH during the pH swing times, i.e., by a controlled pH swing, on the morphology of the TiO₂ particles was investigated. The photocatalytic properties of the TiO₂ catalysts prepared by controlled pH swing were compared with TiO₂ particles prepared without adjusting the pH during the swing times. The photocatalytic degradation reaction of these TiO₂ catalysts was investigated by comparing their effectiveness in 2-propanol oxidation. The experimental results showed that the TiO₂ photocatalysts prepared without adjusting the pH performed better in controlling the important parameters of the catalysts such as particle size, surface area, anatase/rutile phase ratio and pore size, as well as pore volume than the TiO₂ photocatalysts prepared by a controlled pH swing method. Deceased.     

Photocatalytic characteristics of TiO2 supported on SiO2

The photocatalytic decomposition of acetaldehyde was carried out on TiO₂/SiO₂. The presence of a support (SiO₂) in TiO₂/SiO₂ helped to promote the efficiency of the photocatalyst. The silica support enhanced the effective surface area of TiO₂ and adsorption of acetaldehyde on TiO₂/SiO₂. TiO₂/SiO₂ synthesized from Ti(SO₄)₂ showed promoting effect on acetaldehyde decomposition. The XPS results revealed that TiO₂/SiO₂ prepared with Ti(SO₄)₂ generated SO ₄ ^2? sites on the TiO₂ surface. The increased acidity could promote the adsorption of acetaldehyde and photocatalytic degradation of acetaldehyde. The sulfate ion seemed to generate the bifunctional sites (acid sites and photoactive sites) and promoted the acetaldehyde decomposition on TiO₂/SiO₂.     

Ethanol to Acetaldehyde Conversion under Thermal and Microwave Heating of ZnO-CuO-SiO2 Modified with WC Nanoparticles

The nonoxidative conversion of ethanol to acetaldehyde under thermal and microwave heating was studied on mixed oxide ZnO-CuO-SiO₂ catalysts modified with additives of tungsten carbide nanoparticles. The results revealed that the WC-modified catalyst exhibited superior activity and selectivity under microwave heating conditions. It is assumed that when microwave heating is used, hot zones can appear at the contact points of WC nanoparticles and active centers of the mixed oxide ZnO-CuO-SiO₂ catalyst, which intensively absorb microwave energy, allowing the more efficient formation of acetaldehyde at moderate temperatures. Thermodynamic calculations of equilibrium concentrations of reagents and products allowed us to identify the optimal conditions for effective acetaldehyde production. The initial catalyst and the catalyst prepared by the coprecipitation of the oxides with the addition of WC were characterized by physicochemical methods (TPR-H₂, XRD, DRIFTS of adsorbed CO). The active centers of the oxide catalyst can be Cu⁺ cations.     

Microwave‐Hydrothermal Preparation and Visible‐Light Photoactivity of Plasmonic Photocatalyst Ag‐TiO2 Nanocomposite Hollow Spheres

Visible‐light‐driven plasmonic photocatalyst Ag‐TiO₂ nanocomposite hollow spheres are prepared by a template‐free chemically‐induced self‐transformation strategy under microwave‐hydrothermal conditions, followed by a photochemical reduction process under xenon lamp irradiation. The prepared samples are characterized by using scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, N₂ adsorption‐desorption isotherms, X‐ray photoelectron spectroscopy, UV/Vis and Raman spectroscopy. Production of ?OH radicals on the surface of visible‐light illuminated TiO₂ was detected by using a photoluminescence method with terephthalic acid as the probe molecule. The photocatalytic activity of as‐prepared samples was evaluated by photocatalytic decolorization of Rhodamine B (RhB) aqueous solution at ambient temperature under visible‐light irradiation. The results show that the surface plasmon absorption band of the silver nanoparticles supported on the TiO₂ hollow spheres was red shifted, and a strong surface enhanced Raman scattering effect for the Ag‐TiO₂ nanocomposite sample was observed. The prepared nanocomposite hollow spheres exhibits a highly visible‐light photocatalytic activity for photocatalytic degradation of RhB in water, and their photocatalytic activity is higher than that of pure TiO₂ and commercial Degussa P25 (P25) powders. Especially, the as‐prepared Ag‐TiO₂ nanocomposite hollow spheres at the nominal atomic ratio of silver to titanium ( R ) of 2 showed the highest photocatalytic activity, which exceeds that of P25 by a factor of more than 2.     

Characteristics of microwaves on second generation nitrogen-doped TiO2 nanoparticles and their effect on photoassisted processes

Characteristics of 2.45-GHz microwave radiation were examined on two second generation nitrogen-doped TiO₂ nanomaterials prepared by annealing Degussa P-25 TiO₂ and Ishihara ST-01 TiO₂ at 400 °C and 500 °C, respectively, in air in the presence of urea, and for comparison on the undoped pristine samples. Band gaps of all four samples were determined by diffuse reflectance spectroscopy. Both the sizes and the BET specific surface areas of the TiO₂ particles were determined, together with dielectric constants and dielectric loss factors. Nitrogen doping caused the size to increase and surface area to decrease. Temperature–time profiles showed that the heating efficiency of the N-doped specimens by the microwaves was greater, particularly significant for the N-doped P25 sample, but rather small for the N-ST01 sample. The effect of microwaves on the surface optical phonons of the samples, with and without UV–vis irradiation, was examined by an in situ Raman spectroscopic technique; for the undoped P-25 and nitrogen-doped N-P25 TiO₂ systems the effect was negligible. By contrast, microwave irradiation of Ishihara ST-01 and nitrogen-doped N-ST01 TiO₂ samples showed significant changes in the 144-cm^?1 optical phonons. Results infer a microwave thermal effect on the Ishihara ST-01 and N-ST01 specimens, whereas for the Degussa P-25 samples the microwaves also imparted a specific effect as the microwaves influenced the N-dopant sites in contrast to the ST-01 systems where the dopant sites were unaffected as evidenced by temperature–time profiles. The microwave-/photo-assisted degradation of 4-chlorophenol under various conditions of UV–vis irradiation and conventional heating, as opposed to microwave heating, confirms the specific microwave effect for the P-25 systems.     

Efficient preparation of nanocrystalline anatase TiO2 and V/TiO2 thin layers using microwave drying and/or microwave calcination technique

This study has demonstrated that the synthesis of TiO₂ and V/TiO₂ thin layers may be significantly improved and extended if microwave energy is employed during the drying and/or calcination step. Thin nanoparticulate titania layers were prepared via the sol-gel method using titanium n-butoxide as a precursor. As prepared films were then analyzed by means of various characterization techniques (Raman spectroscopy, UV/Vis, AFM, XPS) in order to determine their functional properties. The photocatalytic activities of prepared layers were quantified by the decoloring rate of Rhodamine B. All thermal treatments in microwave field were done in the same manner, by using an IR pyrometer in the microwave oven and monitoring the temperature of the heating. Nevertheless the microwave and thermally prepared materials were different. This in turn may lead to differences in their functional and also photocatalytic properties.     

A comparative study on characterization and photocatalytic activities of gadolinium–boron codoped and mono-doped TiO2 nanoparticles

Gadolinium?Cboron codoped and mono-doped TiO₂ nanoparticles were prepared using a sol?Cgel method, and tested for photocatalytic activity by the UV light after a further calcination process. For comparison, a pure TiO₂ sample was also prepared and tested under the same conditions. The prepared catalysts were characterized by X-ray diffraction, scanning electron microscope, and UV?CVis spectra. The photocatalytic activity of the samples was evaluated through the photo-degradation of three different dyes under UV light. The experiments demonstrated that the gadolinium?Cboron codoped TiO₂ (Gd?CB?CTiO₂) sample calcined at 500?°C possessed the best photocatalytic activity, and the photodegradation rate of the Reactive Brilliant Red K2G aqueous solution could reach to 95.7% under UV irradiation for 80?min. The results showed that Gd?CB?CTiO₂ has smaller crystallite size and higher photocatalytic activity than that of mono-doped TiO₂ samples and undoped TiO₂.     

N,S共掺杂纳米TiO_2:水解-溶剂热法合成及可见光催化活性

采用简单的两相分离的水解-溶剂热法,以硫脲为非金属原料,可控地制备了N,S共掺杂的纳米TiO2。所获得的纳米TiO2平均粒径为10 nm、粒径分布集中,且分散性好。N,S共掺杂拓展了纳米TiO2对可见光的响应范围。气氛可控的表面光电压谱(SPS)的测试结果表明,N,S共掺杂引起的表面态能够捕获光生空穴,进而有利于光生电荷分离。在可见光催化氧化水产氧及降解污染物乙醛的过程中,共掺杂的纳米TiO2表现出了高的活性,甚至优越于N掺杂的。这主要归因于N,S共掺杂的纳米TiO2分散性好、可见光吸收强和光生电荷分离高。