Synthesis and photocatalytic applications of Ag/TiO2-nanotubes

TiO₂- and Ag/TiO₂-nanotubes (NTs) were synthesized by hydrothermal methods and microwave-assisted preparation, respectively. Scanning electron microscopy, high resolution transmission electron microscopy, Brunauer-Emmett-Teller particle surface area measurement and X-ray diffraction were used to characterize the nanotubes. Rutile TiO₂-NTs with Na₂Ti₅O₁₁ crystallinity had a length range of 200-400 nm and diameters of 10-20 nm. TiO₂- and Ag/TiO₂-NTs with a 0.4% deposition of Ag had high surface areas of 270 and 169 m² g⁻¹, respectively. The evaluation of photocatalytic activity showed that Ag/TiO₂-NTs displayed higher photocatalytic activity than pure TiO₂-NTs and a 60.91% degradation of Rhodamine-B with 0.8% deposition of Ag species. Also 60% of Rhodamine-6G was physisorbed and 40% chemisorbed on the surface of TiO₂-NTs. In addition, the photocatalytic degradations of organochlorine pesticides taking α-hexachlorobenzene (BHC) and dicofol as typical examples, were compared using Ag/TiO₂-NTs, and found that their degradations rates were all higher than those obtained from commercial TiO₂.     

Synthesis,Characterization, and Photocatalytic Properties of Ag/TiO2 Composite Nanofibers Prepared by Electrospinning

Ag nanoparticles (Ag NPs) embedded titanium dioxide (TiO₂) nanofibers were fabricated by colloidal sol process, electrospinning, and calcination technique. Calcination of the electrospun nanofibers were heat treated at 600°C for 180 minutes in air atmosphere. X-ray diffraction patterns exhibited that the anatase phase and silver coexisted in the resulted Ag NPs/TiO₂ nanofibers; transmission electron microscopy demonstrated Ag NPs well spread in the porous microstructure of composite fibers. The prepared nanofibers were utilized as photocatalyst for degradation of methyl orange. The degradation rate of methyl orange dye solution containing Ag/TiO₂ composite nanofibers is 99% only after irradiation for 3 hours. It is proposed that these new Ag NPs/TiO₂ composite nanofibers will have potential application in water pollution treatment.      

High photocatalytic activity and stability for decomposition of gaseous acetaldehyde on TiO2/Al2O3 composite films coated on foam nickel substrates by sol-gel processes

A set of anatase titanium dioxide (TiO₂) films coated on foam nickel that modified by Al₂O₃ films as transition layer (indicated as TiO₂/Al₂O₃ films) were synthesized via sol-gel route. The bulk and surface properties of the TiO₂/Al₂O₃ films were characterized by thermal gravimetric and differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), and BET. The photocatalytic activities of TiO₂/Al₂O₃ films were investigated based on the degradation of gaseous acetaldehyde under ultraviolet (UV) irradiation. The foam nickel is a promising substrate material in practical applications because of its excellent hydrodynamic properties for gas passing. The TiO₂/Al₂O₃ composite films showed much higher photocatalytic activity and stability for degradation of gaseous acetaldehyde than the onefold TiO₂ films. The significant enhancement in photocatalytic activity and stability can be ascribed to the coating of Al₂O₃ transition layer, which concentrates the target substances around TiO₂ particles and increases the specific surface area (SSA) of the substrate (the SSAs of bare foam nickel and Al₂O₃ modified foam nickel are 0.12 and 113.7 m²/g, respectively) to provide more sites for TiO₂ loading.     

CTAB辅助合成纳米复合材料Ag/ZnO-TiO2及其紫外光催化性能

在模板剂溴化十六烷基三甲基胺(CTAB)的辅助作用下,按nAg∶nZn∶nTi=0.1∶2∶1的物质的量的比,采用溶胶-凝胶再结合程序升温溶剂热法制备了一系列纳米复合材料Ag/ZnO-TiO2(CTAB),并经X射线衍射(XRD)、紫外-可见漫反射吸收光谱(UV-Vis/DRS)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)、扫描电子显微镜配合X射线能量色散谱仪(SEM-EDS)和N2吸附-脱附测定等测试手段对不同温度(500、600、700℃)和不同时间(5、7 h)下煅烧得到各产物的组成、结构及形貌等进行了表征。结果表明,该系列复合材料不仅含有ZnO纤锌矿和TiO2锐钛矿结构,同时有部分Zn2TiO4生成,其Ag还以单质形式存在。在CTAB作用下改变煅烧温度和时间可使各产物分别呈现纳米线、纳米球等多种形态,且颗粒分布较均匀。上述各复合材料在紫外光作用下对罗丹明B(RB)的光催化降解结果显示,样品煅烧温度和煅烧时间不同,其活性会发生明显的变化。     

ZnFe2O4/Ag/TiO2复合材料的制备及其光催化性能

以硝酸银、钛酸四丁酯、无水氯化锌、六水氯化铁为原料,采用溶胶-凝胶法与溶剂热相结合的方法制备了ZnFe₂O₄/Ag/TiO₂复合材料,通过扫描电子显微镜、能谱分析仪、X射线粉末衍射仪、X射线光电子能谱仪、振动样品磁强计、紫外可见分光光度计对样品进行表征及测试。结果表明： ZnFe₂O₄/Ag/TiO₂-10具有最佳的光催化效果,在紫外和可见光下对染料的降解率都能达到90%以上,具有优异的紫外可见光光催化活性。ZnFe₂O₄/Ag/TiO₂具有独特的磁性,能在外部磁场作用下进行回收利用,这使其在实际应用中成为可能。通过磁分离技术重复回收利用5次后仍然保持优良的光催化性能,说明ZnFe₂O₄/Ag/TiO₂-10具有优异的磁性及较高的光催化循环稳定性。     

ZnFe2O4/Ag/TiO2复合材料的制备及其光催化性能

以硝酸银、钛酸四丁酯、无水氯化锌、六水氯化铁为原料,采用溶胶-凝胶法与溶剂热相结合的方法制备了ZnFe₂O₄/Ag/TiO₂复合材料,通过扫描电子显微镜、能谱分析仪、X射线粉末衍射仪、X射线光电子能谱仪、振动样品磁强计、紫外可见分光光度计对样品进行表征及测试。结果表明：ZnFe₂O₄/Ag/TiO₂-10具有最佳的光催化效果,在紫外和可见光下对染料的降解率都能达到90%以上,具有优异的紫外可见光光催化活性。ZnFe₂O₄/Ag/TiO₂具有独特的磁性,能在外部磁场作用下进行回收利用,这使其在实际应用中成为可能。通过磁分离技术重复回收利用5次后仍然保持优良的光催化性能,说明ZnFe₂O₄/Ag/TiO₂-10具有优异的磁性及较高的光催化循环稳定性。     

退火气氛对掺银TiO2薄膜结构和光催化性能的影响

本文采用sol-gel法制备了掺银的TiO2/glass纳米光催化薄膜,并分别在空气和真空条件下对薄膜进行退火处理, 结构和光催化性能的测试结果表明, 退火气氛对薄膜的结构和薄膜对染料溶液的光催化降解效率都有影响。经真空退火处理的TiO2及Ag-TiO2薄膜较空气中退火处理的同样薄膜的光催化性能都低, 但适量掺银的Ag-TiO2薄膜的光催化活性较TiO2有不同程度的增强。     

Patterning Effect of a Sol-Gel TiO2 Overlayer on the Photocatalytic Activity of a TiO2/SnO2 Bilayer-Type Photocatalyst

TiO₂ films with a thickness of 75 ± 5 nm (anatase) were formed on SnO₂-film (580 ± 80 nm) coated soda-lime glass substrates (SnO₂/SL-glass) by a sol-gel method. Although the photocatalytic activity for CH₃CHO oxidation (_ex > 300 nm) significantly exceeded that of a standard TiO₂/quartz sample, it decayed with illumination time (t) at t > 0.75 h. Stripes of anatase TiO₂ films of 40 nm in thickness and 1 mm in width were prepared on the SnO₂/SL-glass substrate in a 1-mm pitch by photolysis of an organically modified sol-gel film. The TiO₂ patterning further increased the photocatalytic activity by a factor of 4.1 as compared to the non-patterned sample, and it was also maintained at 0 < t < 2 h. The flat band potentials of the TiO₂ and SnO₂ films are determined to be –0.34 and +0.07 V (vs. SHE), respectively, at pH = 7 by the Mott-Schottky plots. On the basis of the results, the outstanding patterning effects could be rationalized in terms of the vectorial charge separation at the interface between TiO₂ and SnO₂.     

Ag/TiO2光催化还原硝酸氮

利用化学还原法制备不同Ag掺杂量TiO₂纳米催化剂,采用TEM、XRD、XRF和UV-Vis对催化剂进行表征。考察了催化剂在紫外光(254 nm)和可见光照射下还原初始浓度100 mgN·L^-1水相硝酸氮的活性和效果。重点考察了紫外光照射下Ag掺杂量、不同空穴捕获剂(甲酸、甲醇、乙酸、乙醇、草酸、草酸钠等)及甲酸浓度对硝酸氮还原的影响;对硝酸氮转化率和总氮去除率、形成亚硝酸氮、氨氮浓度及氮气选择性的影响。甲酸浓度为0.030 mol·L^-1、Ag掺杂量为1.0wt%时催化剂效果最佳。此时,硝酸氮、总氮的转化率分别为98.43%、78.13%;亚硝酸氮浓度为零,转化的硝酸氮中只有20.76%转化为氨氮,氮气选择性为79.24%。可见光下进行光催化还原反应时,硝酸氮转化率仅37.98%,但氮气的选择性较高。     

Low-temperature synthesis of photocatalytic TiO2 thin film from aqueous anatase precursor sols

Anatase TiO₂ sols (RS) were synthesized by peptizing the hydrolysis of titanyl sulfate in abundant hydrogen peroxide solution and subsequent reflux to enhance crystallization. The influences of various reflux time on crystallinity, morphology, and size of the obtained TiO₂ sol and dried TiO₂ film particles were investigated. At room temperature, crystalline TiO₂ thin film was deposited on glass silde from the as prepared TiO₂ sol by dip-coating method. No further thermal posttreatment was required to eliminate organics from the film or to induce titania crystallization. TiO₂ thin film on substrates could be thickened by means of consecutive dip-coating process. Titania film thus obtained was transparent and showed proper adherence. The photocatalytic activities of the TiO₂ thin film was assessed by the degradation of methyl orange in aqueous solution. The preparation process of photocatalytic TiO₂ thin film was quite simple and a low-temperature route.     

钛、铝和玻璃上TiO2光催化膜的失活研究

采用浸渍提拉法，在平行条件下制备了钛、铝和玻璃载体上的TiO₂膜TiO₂ / Ti、TiO₂ / Al和TiO₂ / G，利用X射线光电子能谱(XPS)、原子力显微镜(AFM)和光催化降解实验等手段对膜样品进行了表征和活性评价。实验结果表明，在铝和玻璃基材上制膜时发生了显著的基材元素溢出，使各膜样品的化学组成不同，同时TiO₂粒子和膜表面形貌也因前驱物烧结行为不同而差异较大。TiO_{2相似文献}   

Photodecomposition of methylene-blue by highly-dispersed nano TiO2/Ag catalyst

A highly dispersed nano-TiO₂/Ag catalyst is synthesized in an alkaline solution. The photocatalytic activity required for the removal of dimethyl-blue is enhanced with the effectiveness of dispersion and the proportion of nano-TiO₂.     

Effect of dopant concentration on photocatalytic activity of TiO2 film doped by Mn non-uniformly

The thin films of TiO₂ doped by Mn non-uniformly were prepared by sol-gel method under process control. In our preceding study, we investigated in detail, the effect of doping mode on the photocatalytic activity of TiO₂ films showing that Mn non-uniform doping can greatly enhance the activity. In this study we looked at the effect of doping concentration on the photocatalytic activity of the TiO₂ films. In this paper, the thin films were characterized by UV-vis spectrophotometer and electrochemical workstation. The activity of the photocatalyst was also evaluated by photocatalytic degradation rate of aqueous methyl orange under UV radiation. The results illustrate that the TiO₂ thin film doped by Mn non-uniformly at the optimal dopant concentration (0.7 at %) is of the highest activity, and on the contrary, the activity of those doped uniformly is decreased. As a comparison, in 80 min, the degradation rate of methyl orange is 62 %, 12 % and 34 % for Mn non-uniform doping film (0.7 at %), the uniform doping film (0.7 at %) and pure titanium dioxide film, respectively. We have seen that, for the doping and the pure TiO₂ films, the stronger signals of open circuit potential and transient photocurrent, the better photocatalytic activity. We also discusse the effect of dopant concentration on the photocatalytic activity of the TiO₂ films in terms of effective separation of the photon-generated carriers in the semiconductor.     

Effects of doping La and Cu on photoinduced charge properties of TiO2 and its relationships with photocatalytic activity

The pure, 1 mol% only La or only Cu doped TiO₂ and La and Cu codoped TiO₂ were prepared by a sol-gel process. The effects of doping on photoinduced charge properties of nanosized TiO₂ were mainly investigated by means of Surface Photovoltage Spectrum (SPS) and Photoluminescence Spectrum (PL), together with their relationships with photocatalytic activity. The results show that La dopant can inhibit the phase transformation of TiO₂, meanwhile improve the separation rate of photoinduced charge carriers, and enrich the binding surface states. However, Cu dopant has a reverse effect compared to La dopant. This is responsible for the results that doping La is favorable for the increase in the photocatalytic activity for degrading the RhB solution, while doping Cu is bad to photocatalyitc reaction. In addition, codoping La and Cu cannot exhibit an obvious combination effect.     

High photocatalytic degradation activity of polyethylene containing polyacrylamide grafted TiO2

A novel photocatalytic polyacrylamide grafted TiO₂ (PAM-g-TiO₂) nanocomposite was prepared and embedded into a low density polyethylene (LDPE) plastic. Photocatalytic degradation of the LDPE/PAM-g-TiO₂ composite film was carried out under ambient conditions under ultraviolet light irradiation. The properties of composite film were compared with those of the pure LDPE film by measuring the changes in weight loss, carbonyl index, molecular weight, tensile strength and elongation at break. PAM-g-TiO₂ embedded LDPE showed highly enhanced photocatalytic degradation. Irradiating the LDPE/PAM-g-TiO₂ composite film for 520 h under UV light reduced its weight by 39.85% and average molecular weight (M_w) by 94.60%, while that of pure LDPE film was only 1.03% and 69.59%, respectively. The addition of PAM-g-TiO₂ brought about the good dispersion of TiO₂ in LDPE matrix and improved the hydrophilicity of composite film, which were able to facilitate the degradation of LDPE. The photocatalytic degradation mechanism of the films is briefly discussed.     

玻璃微珠/Ag/TiO2可见光催化剂的制备与表征

通过离子交换法将Ag纳米颗粒负载于玻璃微珠的表面及浅表层,并以钛酸四丁酯的乙醇溶液为前驱体,将TiO₂负载于包含银的玻璃微珠表面,制得一种玻璃微珠/Ag/TiO₂复合光催化剂。由于纳米银的表面等离子体吸收效应,该复合光催化剂具有一定的可见光响应特性。利用XRD、SEM对样品进行表征,可发现玻璃微珠表面形成一层均匀多孔的锐钛矿TiO₂,其粒径均在50 nm左右。由漫反射光谱可得出该催化剂具有较强的可见光吸收,并在降解甲基橙溶液的试验中表现出较好的可见光催化活性。     

Visible-light-mediated facile synthesis of disulfides using reusable TiO2/MoS2 nanocomposite photocatalyst

A nontoxic and inexpensive TiO₂/MoS₂ nanocomposite was prepared and employed as an efficient photocatalyst for the synthesis of symmetrical disulfides under visible light irradiation at room temperature. Both aryl and alkyl thiols survived the reaction conditions, affording the corresponding disulfides in good to excellent yields. The photocatalyst could be easily recovered by simple centrifugation and filtration and reused several times without significant loss in its activity.     

Comparison of CO2 Reduction Performance with NH3 and H2O between Cu/TiO2 and Pd/TiO2

The aim of this study is to clarify the effect of doped metal type on CO₂ reduction characteristics of TiO₂ with NH₃ and H₂O. Cu and Pd have been selected as dopants for TiO₂. In addition, the impact of molar ratio of CO₂ to reductants NH₃ and H₂O has been investigated. A TiO₂ photocatalyst was prepared by a sol-gel and dip-coating process, and then doped with Cu or Pd fine particles by using the pulse arc plasma gun method. The prepared Cu/TiO₂ film and Pd/TiO₂ film were characterized by SEM, EPMA, TEM, STEM, EDX, EDS and EELS. This study also has investigated the performance of CO₂ reduction under the illumination condition of Xe lamp with or without ultraviolet (UV) light. As a result, it is revealed that the CO₂ reduction performance with Cu/TiO₂ under the illumination condition of Xe lamp with UV light is the highest when the molar ratio of CO₂/NH₃/H₂O = 1:1:1 while that without UV light is the highest when the molar ratio of CO₂/NH₃/H₂O = 1:0.5:0.5. It is revealed that the CO₂ reduction performance of Pd/TiO₂ is the highest for the molar ratio of CO₂/NH₃/H₂O = 1:1:1 no matter the used Xe lamp was with or without UV light. The molar quantity of CO per unit weight of photocatalyst for Cu/TiO₂ produced under the illumination condition of Xe lamp with UV light was 10.2 μmol/g, while that for Pd/TiO₂ was 5.5 μmol/g. Meanwhile, the molar quantity of CO per unit weight of photocatalyst for Cu/TiO₂ produced under the illumination condition of Xe lamp without UV light was 2.5 μmol/g, while that for Pd/TiO₂ was 3.5 μmol/g. This study has concluded that Cu/TiO₂ is superior to Pd/TiO₂ from the viewpoint of the molar quantity of CO per unit weight of photocatalyst as well as the quantum efficiency.     

TiO2/CuS异质结的制备及光催化降解染料废水的研究

以原位沉淀法和水热法混合的合成手段,制备了TiO_2/CuS异质结光催化剂。这种异质结改善了单一TiO_2半导体光催化剂的缺陷,明显提高了太阳光下光催化降解甲基橙的效率。TiO_2与CuS之间形成的异质结结构和合适的能带结构能够扩展材料对太阳光谱的响应范围并且很好地收集和传输光诱导载流子,从而提高了载流子的分离效率,最终使半导体的光催化活性明显增强。结果表明,太阳光照射25min后,相比于TiO_2/MnS、TiO_2/CdS和TiO_2/ZnS异质结,TiO_2/CuS异质结(TiO_2和CuS的摩尔比为3∶1)对甲基橙的降解效果最佳,降解效率能达到97.3%。为提高半导体的光催化活性提供了一条可行的路径。     

Influence of High-energy electron-beam on photocatalytic activity of TiO2 films on carbon-fiber deposited by atomic layer deposition

High-energy electron-beam with energy of 1 MeV was used for modifying surface structure of TiO₂ thin films on carbon fiber prepared by using atomic layer deposition under atmospheric pressure. TiO₂ nanoparticles (∼20 nm) on carbon fiber underwent structural modification of the surface upon electron-beam treatment, resulting in enhanced photocatalytic activity. In contrast, a thicker film of TiO₂ did not show such changes in surface structure and photocatalytic activity by electron-beam treatment. We demonstrate that electron-beam can be used for modifying surface structure of photocatalysts consisting of nanoparticles for improvement of their activity.