波长对Ag/TiO2催化剂上二氧化碳光催化还原的影响

Photocatalytic reduction of CO2 by water was performed in the presence of a Ag/TiO2 catalyst under illumination by lamps with different wavelengths(254,365,and 400 nm).The yields of the main products(methane and methanol)were higher with the 254 nm lamp than with the 365 lamp while no products were observed with the 400 nm lamp.This was because the electron-hole generation rate increased with increasing energy of irradiation(decreasing wavelength)and there were higher densities of electron states at higher energies in TiO2. The increased efficiency of electron-hole generation with a shorter wavelength irradiation increased the efficiency of the catalyst.The energy of the electrons excited by visible light(400 nm)was too low for CO2 photocatalytic reduction.     

浅池型TiO2/ACF光催化降解水中苯酚的研究

为了提高光催化过程的降解速率，本文以涂覆法制得的二氧化钛/活性炭纤维（TiO2/ACF）为光催化剂，300 W(365 nm)高压汞灯为光源，研究了浅池型反应器中苯酚在TiO2/ACF上的光催化降解动力学；探讨了光强度、高压汞灯滤光以及光源种类对降解反应的影响，并对光氧化，光催化和吸附过程进行了比较。结果表明：光氧化对苯酚的降解无效果，光催化降解速率常数与吸附速率常数之比为3.35/1；光强越大，光催化降解速率越快；高压汞灯不滤光时光催化降解速率明显加快，但光催化反应仍遵循准一级反应动力学方程；波长为254 nm紫外杀菌灯的降解效果高于波长为365 nm高压汞灯滤光后的降解效果。     

Wavelength-sensitive photocatalytic degradation of methyl orange in aqueous suspension over iron(III)-doped TiO2 nanopowders under UV and visible light irradiation

Well-crystallized iron(III)-doped TiO2 nanopowders with controlled Fe3+ doping concentration and uniform dopant distribution, have been synthesized with plasma oxidative pyrolysis. The photocatalytic reactivity of the synthesized TiO2 nanopowders with a mean particle size of 50-70 nm was quantified in terms of the degradation rates of methyl orange (MO) in aqueous TiO2 suspension under UV (mainly 365 and 316 nm) and visible light irradiation (mainly 405 and 436 nm). The photodecomposition of MO over TiO2 nanopowders followed a distinct two-stage pseudo first order kinetics. Interestingly, the photocatalytic reactivity depends not only on the iron doping concentration but also on the wavelength of the irradiating light. Under UV irradiation, nominally undoped TiO2 had much higher reactivity than Fe3+ -doped TiO2, suggesting that Fe3+ doping (> 0.05 at. %) in TiO2 with a mean particle size of approximately 60 nm was detrimental to the photocatalytic decomposition of methyl orange. Whereas, under visible light irradiation, the Fe3+ -doped TiO2 with an intermediate iron doping concentration of approximately 1 at. % had the highest photocatalytic reactivity due to the narrowing of band gap so that it could effectively absorb the light with longer wavelength. A strategy for improving the photocatalytic reactivity of Fe3+ -doped TiO2 used in the visible light region is also proposed.     

Investigation of the photocatalytic degradation of organochlorine pesticides on a nano-TiO2 coated film

The photocatalytic degradation of organochlorine pesticides including -, β-, γ-, δ-hexachlorobenzene (BHC), dicofol and cypermethrin were carried out on a nano-TiO₂ coated films under UV irradiation in the air. The photocatalytic conditions, including the amount of TiO₂, irradiation time and the intensity of light were optimized. The pesticides were most effectively degraded under the condition of 2.24 mg/cm² on TiO₂ film and a 400 W UV irradiation of high-pressure mercury lamp with a wavelength of 365 nm. A typical organochlorine pesticide, 20 μg -BHC, was dipped onto the TiO₂ film surface and degraded completely within 20 min. In addition, the photocatalytic degradation pathways on the nano-TiO₂ coated film were discussed.     

Removal of natural organic matter by ultrafiltration with TiO2-coated membrane under UV irradiation

This study investigates the performance of ultrafiltration (UF) by membranes coated with titanium dioxide (TiO2) photocatalyst under ultraviolet (UV) illumination in removing natural organic matter (NOM) and possibly in reducing membrane fouling. Experiments were carried out using heat-resistant ceramic disc UF membranes and humic acids as model substances representing naturally occurring organic matter. Membrane sizes of 1, 15, and 50 kDa were used to examine the effects of coating under ultraviolet irradiation. A commercial humic solution was subjected to UF fractionation (batch process); gel filtration chromatography was applied to study the effects of molecular weight distribution of NOM on UF membrane fouling. When compared to naked membranes, UV254 (ultraviolet light of lambda=254 nm) illumination of TiO2-coated membranes exhibits more flux decline with similar effluent quality. Although the UF membrane is able to remove a significant amount of humic materials, the incorporated photocatalysis results in poor performance in terms of permeate flux. The TiO2-coated membrane under UV254 irradiation alters the molecular weight (MW) distribution of humic materials, reducing them to <1 kDa, which is smaller than the smallest (1-kDa) membrane in this study. Thus, TiO2-coated membranes under UV254 irradiation do not perform any better in removing natural organic matter and reducing membrane fouling.     

苯乙酮的TiO2光催化降解及其影响因素

在TiO2(Degussa P25)和波长大于350 nm的光作用下,水中苯乙酮(1×10-5～1×10-4mol／L)能发生光催化降解,生成邻羟基苯乙酮等中间产物.该降解过程遵循Langmuir-Hinshelwood动力学方程,降解速率随入射光强度的增强和溶液起始pH值的增大而增大,但反应温度的影响较小,其降解反应的表观活化能为4.2～6.4 KJ/mol.     

Photocatalytic intercalated material based on HLaNb_2O_7 as host and Cd_(0.8)Zn_(0.2)S as guest

A novel photocatalytic material (Pt,Cd0.8Zn0.2S)/HLaNb2O7 was fabricated by successive intercalation and exchange reactions. The (Pt,Cd0.8Zn0.2S)/HLaNb2O7 possessed a gallery height less than 0.5 nm and showed a broad absorption with wavelength over 370―500 nm. Using (Pt,Cd0.8Zn0.2S)/HLaNb2O7 as catalyst, the photocatalytic H2 evolution was more than 160 cm3·h-1·g-1 in the presence of Na2S as a sacrificial agent under irradiation with wavelength more than 290 nm from a 100-W mercury lamp. Furthermore, the catalyst showed photocatalytic activity even under visible light irradiation.     

Highly active TiO2N photocatalysts prepared by treating TiO2 precursors in NH3/ethanol fluid under supercritical conditions

N-doped TiO2 photocatalysts were prepared by pretreating the TiO2 precursor in NH3/ethanol fluid under supercritical conditions, denoted as TiO2N(SC). In contrast to the TiO2N(DC), obtained via direct calcination in which the N dopants were mainly present in the form of surface adsorbed NH3 molecules, most N dopants in the TiO2N(SC) were present in O-Ti-N and N-Ti-N nitrides, as confirmed by either the X-ray photoelectron spectroscopy (XPS) and or the Fourier transform infrared (FTIR) spectra. During liquid-phase oxidative degradation of phenol under irradiation with UV light characteristic of 365 nm, the TiO2N(SC) exhibited much higher activity than either the TiO2N(DC) or the TiO2(SC), i.e., the undoped TiO2 obtained under SCs. According to various characterizations including X-ray diffraction, transmission electron microscopy, FTIR, Brunauer-Emmett-Teller, XPS, and UV-vis diffuse reflectance spectra, the higher activity of the TiO2N(SC) could be attributed to its higher surface area, larger pore volume, well-crystallized anatase, and stronger absorbance of light with longer wavelength. Meanwhile, the OH species resulted from the nitridation of TiO2 could supply more HO* radicals, which were considered as powerful oxidants during phenol degradation. Furthermore, the electron-deficient nitrogen atoms in O-Ti-N nitrides could also account for the higher activity since it could inhibit the recombination between the photoinduced electrons and holes by capturing the photoinduced electrons. The activity of the TiO2N(SC) first increased and then decreased with the increase of the N-content. The TiO2N(SC)-1 with N/Ti molar ratio of 1.73% exhibited maximum activity, which was even much higher than P-25.     

利用TiO2/SO42-光触媒催化还原CO2之参数影响与反应路径探讨

将改良式溶胶-凝胶法制备的酸性触媒TiO2/SO24-涂布于不锈钢网上,并利用自行设计之批次式光催化反应器,在三组近紫外灯管(波长为365nm,光强度为2.0mW/cm2)照射下,进行CO2光催化还原反应操作参数(还原剂种类、CO2初始浓度和反应温度)之影响研究.结果显示,使用氢气为还原剂可获得最高的光催化还原速率,光还原反应之主要气态产物为CO和甲烷,其次为微量的乙烯与乙烷.同时,光催化还原速率亦随着CO2初始浓度及反应温度的提高而增加.FT-IR光谱分析发现,TiO2/SO42-光触媒表面有甲酸、甲醇、碳酸盐、甲酸盐及甲酸甲酯等产物之存在.TiO2/SO42-光触媒催化还原CO2有两种可能反应路径,其中一种反应路径生成CO,CH4,C2H4及C2H6等气态产物;而另一种反应路径则生成CO23a-ds,CH3OHads,HCOOa-ds,HCOOHads,HCOHads与HCOOCH3ads等吸附在光触媒表面的产物.     

Antireflection and self-cleaning properties of a moth-eye-like surface coated with TiO2 particles

Poly(ethylene terephthalate) (PET) films with a moth-eye-like surface are coated with TiO(2) particles to form self-cleaning antireflective films. The use of a TiO(2) suspension of high concentration to coat the PET surface produces a thicker TiO(2) layer with smaller pores, whereas a low concentration of a TiO(2) suspension gives a thinner layer of TiO(2) with larger pores. The PET films coated with TiO(2) particles exhibit a high transmittance of 76-95% and almost no absorption in the range of 400-800 nm. The PET films coated with a TiO(2) suspension with a concentration of ≥2 vol % exhibit superhydrophilicity after irradiation with UV light. After irradiation, the superhydrophilic nature is retained for at least 18 days. The TiO(2)-coated PET films showed the ability to decompose methylene blue under UV irradiation.     

CdS/TiO2光催化去除水体中氨氮的研究

利用溶胶-凝胶法制备了不同比率的CdS掺杂TiO₂复合纳米颗粒催化剂,并用其进行了紫外光、日光灯和太阳光全波长光催化去除水中氨氮和其它形式无机氮的对比实验研究.考察了添加催化剂的量、CdS复合比率、有氧化态氮亚硝酸根或硝酸根与氨氮共存时光催化脱氮的耦合效果、外加光源等对脱除氨氮效率的影响,并研究了后3个因素对CdS光腐蚀程度的影响.对于氨氮初始质量浓度为50mg/L的模拟废水,在通空气搅拌条件下,n(CdS):n(TiO₂)=0.17的CdS/TiO₂催化剂脱氮效果最佳,此时经紫外光照2h后脱除氨氮效率达41.5%.实验结果表明:复合催化剂中CdS的含量是影响光催化活性和光腐蚀程度的重要因素.     

Pt/TiO2上苯和乙烯光催化氧化过程的磁场效应

以Pt/TiO₂为催化剂和365 nm紫外光为光源, 在低于0.2 T的磁场强度范围考察了磁场对苯和乙烯光催化氧化反应的影响. 实验发现, 当用紫外灯管作光源并靠近磁场磁极或者置于磁场磁极间隙内照射反应器时, 磁场可显著提高气相苯和乙烯的光催化转化率和矿化率; 而当光源远离磁场磁极而通过光导纤维传导照射到反应器上时, 磁场对这两个反应没有促进作用. 在前一种情况下, 紫外灯管的发光强度随磁场的增强而提高, 磁场对这两个光催化降解反应的促进作用被证实是由于磁场提高了紫外灯管的发光强度, 进而为反应提供了更多的光能和使反应温度升高所致；在后一种光照方式下, 由于光源不受磁场影响, 磁场对这两个光催化反应不产生影响. 这一研究结果表明, 在所研究磁场强度范围, 磁场对气-固相光催化反应没有任何本征影响.     

Mg-Al 类水滑石/二氧化钛异质复合纳米晶光催化氧化苯的性能

 采用过饱和沉淀法合成 n(Mg)/n(Al) = 2 的 Mg-Al 类水滑石化合物 (Mg-Al-HT), 再用水热法将它与钛胶复合, 制得 Mg-Al-HT/TiO2 异质复合光催化剂. 采用 X 射线粉末衍射、透射电子显微镜、场发射扫描电子显微镜、低温 N2 吸附-脱附、紫外-可见漫反射光谱和热重等技术对催化剂结构、成分和性质进行了表征. 结果表明, 在波长 365 nm 的紫外光照射降解苯的反应中, Mg-Al-HT/TiO2 异质复合光催化剂表现出优于单一的 TiO2 或 Mg-Al-HT 催化剂的光催化活性, 且稳定性更高; 同时讨论了该复合催化剂性能优异的原因. 另外, 运用电子顺磁共振技术检测到体系中存在羟基自由基等活性物种, 并据此提出了 Mg-Al-HT/TiO2 异质复合纳米晶催化剂光催化降解苯的反应机理.     

光催化微反应器中水样光催化降解及Cd2+在线检测

本文以粉末法制备TiO₂涂层的玻璃微流控芯片作为光催化反应器,采用UV-LED点光源为紫外光源,实现了水样中EDTA的光催化降解,并用铋膜电极差分脉冲溶出伏安法在线检测微量水样中的重金属离子Cd²⁺。水样中的Cd²⁺由于EDTA的络合作用无法在铋膜电极上产生电流信号,而当水样在光催化微反应器中经紫外光催化后,由于EDTA与Cd²⁺的配合物结构遭破坏,因此释放出游离的Cd²⁺,从而使Cd²⁺的电流信号得到一定程度的恢复。Cd²⁺的电流恢复程度越大,表明EDTA被光催化降解的程度越高。本文考察了光照强度、反应液流速和氧气流速、pH等因素对EDTA光催化降解效率的影响。在光照强度为120 mW/cm²、反应液流速为50 μL/h、氧气流速为850 μL/h、pH为4.4条件下,水样中EDTA的光催化降解率效果最佳,水样中Cd²⁺的电流恢复程度可达92.6%。反应液流速为300 μL/h时,Cd²⁺的电流恢复率为60.0%,重复光催化反应5次的RSD为5.2%,具有较好的重现性。本文建立了水样EDTA光催化降解及Cd²⁺在线检测的微分析系统,在线检测所需的样品体积仅为0.3 mL,完成一个水样分析的时间约为60 min。     

TiO2光催化薄膜在陶瓷器具上抗菌效果的研究

抗菌薄膜;TiO2光催化薄膜在陶瓷器具上抗菌效果的研究     

TiO2薄膜的Ag改性及光催化活性

 用光化学沉积法对纳米TiO2薄膜进行了Ag改性,用漫反射紫外-可见光谱、扫描电子显微镜和X射线光电子能谱分析了Ag-TiO2薄膜的光谱特征、表面形貌和表面组成. 以苯酚为模拟污染物,在不同波长光源及有氧和无氧条件下考察了Ag-TiO2薄膜的光催化活性. 结果表明,当银沉积量大于 0.0150 mg/cm2时, Ag-TiO2薄膜对紫外光的吸收发生了明显的蓝移,同时在346 nm附近出现了小的吸收峰且该峰随着银沉积量的增加逐渐向长波方向移动. 沉积在TiO2薄膜表面的银颗粒大小不均匀,主要以单质银的形式存在,也生成了部分Ag2O; 相对于TiO2薄膜, Ag-TiO2薄膜表面吸附氧的含量明显增大. Ag-TiO2薄膜的光吸收特性对其催化活性影响较大. 在低压汞灯及有氧参与的条件下,银沉积量为0.0523 mg/cm2的Ag-TiO2薄膜的催化活性最高, 其反应速率常数是TiO2薄膜的1.16倍. Ag+更易沉积在较大n值的Ag簇上,其颗粒大小不可能完全均匀. Ag-TiO2薄膜的光吸收特性、 Ag簇的大小以及Ag对O2的吸附作用是决定Ag-TiO2薄膜催化活性的主要因素.     

Mechanistic studies of the photocatalytic oxidation of trichloroethylene with visible-light-driven N-doped TiO2 photocatalysts

Visible-light-driven TiO2 photocatalysts doped with nitrogen have been prepared as powders and thin films in a cylindrical tubular furnace under a stream of ammonia gas. The photocatalysts thus obtained were found to have a band-gap energy of 2.95 eV. Electron spin resonance (ESR) under irradiation with visible light (lambda > or = 430 nm) afforded the increase in intensity in the visible-light region. The concentration of trapped holes was about fourfold higher than that of trapped electrons. Nitrogen-doped TiO2 has been used to investigate mechanistically the photocatalytic oxidation of trichloroethylene (TCE) under irradiation with visible light (lambda > or = 420 nm). Cl and O radicals, which contribute significantly to the generation of dichloroacetyl chloride (DCAC) in the photocatalytic oxidation of TCE under UV irradiation, were found to be deactivated under irradiation with visible light. As the main by-product, only phosgene was detected in the photocatalytic oxidation of TCE under irradiation with visible light. Thus, the reaction mechanism of TCE photooxidation under irradiation with visible light clearly differs markedly from that under UV irradiation. Based on the results of the present study, we propose a new reaction mechanism and adsorbed species for the photocatalytic oxidation of TCE under irradiation with visible light. The energy band for TiO2 by doping with nitrogen may involve an isolated band above the valence band.     

侧链型偶氮聚合物液晶在不同波长激发条件下的光致取向

合成了聚甲基丙烯酸 (6 [4 (4 氰基偶氮苯 )苯氧基 ]己酯 ) (Poly(6 [4 (4 cyanophenylazo)phenoxy]hexylmethacrylate) (PM6ABCN) ) ,采用溶液挥发法在玻璃载片上成膜 ,研究了薄膜样品在Tg 温度以下的光致取向 .用波长分别为 36 6、40 0和 436nm的偏振光照射 ,发现PM6ABCN薄膜的光致取向过程不仅依赖于光的强度 ,还依赖所使用的偏振光的波长 .在低于Tg 的温度下 ,用波长为 40 0nm ,功率为 2 0mW cm2 的光照射 10 0s可以使样品的取向达到饱和 ,而用 36 6nm的光导致的取向程度要小于 40 0nm和 436nm的光 ,因为 36 6nm的光会在稳态时产生更多数目的cis异构体     

Nanocrystalline TiO2 solar cells sensitized with InAs quantum dots

We report nanocrystalline TiO2 solar cells sensitized with InAs quantum dots. InAs quantum dots of different sizes were synthesized and incorporated in solar cell devices. Efficient charge transfer from InAs quantum dots to TiO2 particles was achieved without deliberate modification of the quantum dot capping layer. A power conversion efficiency of about 1.7% under 5 mW/cm2 was achieved; this is relatively high for a nanocrystalline metal oxide solar cell sensitized with presynthesized quantum dots, but this efficiency could only be achieved at low light intensity. At one sun, the efficiency decreased to 0.3%. The devices are stable for at least weeks under room light in air.     

Extending the photoresponse of TiO2 to the visible light region: photoelectrochemical behavior of TiO2 thin films prepared by the radio frequency magnetron sputtering deposition method

TiO(2) thin films prepared by a radio frequency magnetron sputtering (RF-MS) deposition method were found to show an enhanced photoelectrochemical response in the visible light region. By controlling the temperature and the gaseous medium during the deposition step, it was possible to control the properties of these films. The photoelectrochemical behavior of the sputtered TiO(2) thin films was compared with that of a commercial TiO(2) sample, and the sputtered films showed higher incident photon to the charge carrier generation efficiency (IPCE of 12.6% at 350 nm) as well as power conversion efficiency (0.33% at 1.84 mW/cm(2)) than the commercial TiO(2) sample. Femtosecond transient absorption spectroscopy experiments have revealed that a major fraction of photogenerated electrons and holes recombine within a few picoseconds, thus limiting photocurrent generation efficiency. The mechanistic insights obtained in the present study should aid in designing semiconductor nanostructures that will maximize the charge separation efficiency and extend the response of the large band gap semiconductor TiO(2) into visible light regions.