光催化原位氧化聚合法制备聚吡咯/TiO_2复合材料及其可见光催化降解罗丹明B的性能

在无需引发剂的条件下,通过光催化原位氧化聚合法一步合成了聚吡咯/TiO2纳米复合材料(PPy/TiO2)。采用UV-Vis、XRD、XPS和FTIR技术对吡咯在TiO2表面的聚合过程和复合材料的结构进行了表征。以罗丹明B(RhB)的降解反应研究了PPy/TiO2复合材料的光催化性能。研究表明,紫外光(λ=365nm)激发TiO2形成电子-空穴对,空穴迁移至表面与吸附于TiO2表面的吡咯单体作用,迅速形成吡咯阳离子和低聚体,最终形成聚吡咯并包覆在TiO2的表面。光催化结果表明,PPy/TiO2复合材料可加速RhB在可见光和紫外光下的降解速率,所制备的PPy/TiO2复合材料是一种可应用于光电转化和光催化方面的多功能材料。     

TiO_2-聚吡咯复合材料的制备及光催化性能

采用原位氧化聚合法制备TiO2-聚吡咯复合材料,研究吡咯与TiO2配比对TiO2-聚吡咯复合材料在紫外光和太阳光下光催化降解甲基橙的影响,利用傅里叶红外光谱仪、X射线衍射仪、紫外-可见光谱仪对样品进行表征。结果表明,TiO2-聚吡咯复合材料与纯聚吡咯相比,聚吡咯本征态特征峰和C─N伸缩振动峰峰值都向高波数偏移,TiO2和聚吡咯的复合并不是单纯的物理复合,而是产生了化学作用力;通过改变吡咯的添加量,可以控制聚吡咯在TiO2粉体表面的包覆量,聚吡咯的包覆对TiO2的晶型没有影响;聚吡咯对TiO2的包覆可降低TiO2的禁带宽度至2.90 eV,使TiO2-聚吡咯复合材料可吸收的波长范围拓宽到可见光区,提高复合材料在可见光下的光催化能力;适量的聚吡咯包覆可以提高TiO2-聚吡咯复合材料的光催化活性,以紫外灯作为光源催化降解甲基橙,当吡咯包覆质量分数为0.06时,复合材料的电子-空穴对分离效果最好;以太阳光作为光源催化降解甲基橙,当吡咯包覆质量分数为0.04时,复合材料的光谱拓展效果最好。     

一步水热法制备N,S（F）共掺杂TiO2纳米管及其可见光催化性能

以尿素、硫脲和氟化铵为掺杂物,采用一步水热法制备可见光响应的不同非金属共掺杂TiO2纳米管(TiO2NT)。通过SEM、TEM、XRD、BET、FT-IR、UV-Vis DRS等对样品进行了表征,考察其吸附性能及在模拟太阳光下对甲基橙的降解活性。结果表明,在碱性条件下一步水热法制备的不同非金属共掺杂TiO2NT具有较大的比表面积(193.93 m2/g)和较小的带隙能(2.76eV),非金属共掺杂明显提高了可见光利用率。在可见光辐照下,硫脲掺杂TiO2纳米管(N,S-TiO2NT)复合材料的光催化性能最好,反应100min后甲基橙降解率可达87.4%,降解过程符合一级动力学方程。     

TiO_2/聚苯胺复合材料的合成、结构表征及光催化性能

在室温下,以苯胺为单体、钛酸四丁酯为反应物,通过化学氧化原位聚合和溶胶-凝胶的方法制备了TiO2/聚苯胺复合材料。利用X-射线衍射仪、傅立叶变换红外光谱仪、紫外-可见吸收光谱仪、热失重分析仪等对复合材料表面的微观结构及热稳定性进行了表征。通过光催化降解甲基橙实验评价了TiO2/聚苯胺复合光催化剂在紫外光条件下的光催化活性,实验表明,TiO2/聚苯胺复合材料的催化效率大大提高,特别是TiO2/聚苯胺(质量比例为1/2)复合材料对甲基橙的降解效率最高达到85.7%。     

氮镍共掺杂TiO2纳米管的制备及其光催化性能

为了制备在高温焙烧后能保持良好管形结构的可见光响应的TiO2纳米管,通过NH4Cl水-溶剂热和Ni(NO3)2浸渍法对传统水热法合成的TiO2纳米管进行掺氮和掺镍改性。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外-可见漫反射(UV-vis DRS)和荧光光谱(PL)等方法对样品进行了表征,并以甲基橙(MO)为光催化降解模型,考察了可见光下制备的样品的光催化性能。结果表明,NH4Cl水-溶剂热掺氮处理可提高TiO2纳米管的管状结构的热稳定性;氮镍共掺杂元素之间的协同作用增强了催化剂对可见光的吸收能力,并且能有效地抑制光生电子空穴的复合,Ni/Ti添加量为0.3%的催化剂具有较高的光催化活性。可见光照射210min,氮镍共掺杂TiO2纳米管对MO的可见光降解率比单独氮和镍掺杂的TiO2分别提高了9.1%和21.2%。     

TiO_2纳米管负载纳米金的制备及其在紫外光下的光电性能(英文)

利用直流磁控溅射法制备纳米金颗粒表面改性TiO2纳米管,并通过XRD,FESEM对其结构进行表征.在紫外光下测试其光电效应,结果发现在定电位和动电位下,纳米金改性后的TiO2纳米管产生的光电流都要比未改性的TiO2纳米管大.在定电位下(1.0V),Au/TiO2纳米管产生的光电流为0.4mA,是TiO2纳米管的1.8倍.在动电位下(-1.5～1.5V),当电位达1.5V时,Au/TiO2纳米管产生的光电流为0.75mA,是TiO2纳米管的3.75倍.     

PPy/TiO2纳米复合材料的制备及光催化活性

采用原位聚合的方法合成了聚吡咯/二氧化钛(PPy/TiO2)纳米复合材料,研究了吡咯(Py)与TiO2的比例、氧化剂的种类、掺杂酸的浓度等因素对PPy/TiO2纳米复合材料在太阳光下光催化降解甲基橙的影响,采用透射电镜、紫外-可见漫反射吸收光谱等方法对样品进行了表征.结果表明,PPy/TiO2纳米复合粒子在太阳光下的光催化活性明显高于TiO2纳米粒子,当Py与TiO2的比例为1:100,三氯化铁为氧化剂,1.0mol·L-1盐酸溶液为掺杂剂时PPy/TiO2纳米复合粒子在太阳光下的光催化活性最高;TiO2纳米微粒以及PPy/TiO2纳米复合微粒的粒径均为10～20nm,复合微粒的粒径没有明显的增大,但是减轻了纳米粒子之间的团聚;聚吡咯使TiO2纳米粒子的禁带宽度由3.12eV降低到2.84eV,TiO2纳米粒子的吸收波长拓展到可见光区,有利于TiO2纳米粒子在太阳光下光催化活性的提高.     

PMoV2/PANI/TiO2复合材料的制备及光催化性能

以(NH4)2S2O8为氧化剂,运用化学氧化聚合法在TiO2颗粒表面包覆聚苯胺薄膜,通过静电自组装方法制备了复合光催化材料PMo V2/PANI/TiO2,采用傅里叶变换红外光谱(FT-IR)、紫外-可见吸收光谱(UV-Vis)、X-射线粉末衍射(XRD)、热分析(TG-DTG)、扫描电子显微镜(SEM)等手段对其组成、结构及形貌等进行了表征.结果表明,复合材料具有锐钛矿晶型结构,颗粒分布较均匀,结构也较规整,平均粒径约为68.53nm.聚苯胺敏化拓宽了TiO2的光谱响应范围,复合材料在紫外和可见光区都有较强的吸收,提高了光能的利用率和光生载流子的分离效率.在光催化降解染料甲基紫研究中,该复合材料表现出较好的光催化性能.其活性明显高于市售P25(TiO2),PANI/TiO2,PMoV2和PANI,降解率达97.1％.     

P3HT及CTCHT修饰纳米TiO2的光电性能研究

用光电流作用谱、光电流-电势图等光电化学方法研究了聚3-己基噻吩(P3HT)及3-己基噻吩和2-噻吩甲酸共聚物(CTCHT)修饰纳米结构TiO2电极的光电转换性质。结果表明,经修饰后的纳米TiO2电极光电流明显增强,光电转换效率得到明显提高。在复合膜电极中存在p-n异质结,异质结的存在有利于光生电子-空穴对的分离,降低了电荷的反向复合几率,提高了光电转换效率。     

金属修饰N掺杂TiO2的制备及其光催化性能研究

首先采用热化学法制备纳米管钛酸,然后把金属硝酸盐和尿素均匀分散于纳米管钛酸的表面,再通过高温焙烧的方法制备得到金属修饰的N掺杂TiO2。采用DRS、XRD分别对样品光吸收能力、晶体结构进行了分析,研究了修饰的金属和掺杂N元素对催化剂光谱吸收的贡献。通过紫外光和可见光光照下降解气相丙烯和液相苯酚考察了催化剂的光催化活性,结果表明,金属修饰N掺杂TiO2在可见光照下对丙烯和苯酚都表现出良好的可见光光催化能力。     

Fabrication of PbS nanoparticle-sensitized TiO₂ nanotube arrays and their photoelectrochemical properties

TiO(2) nanotube arrays (NTAs) are modified with PbS nanoparticles by successive ionic layer adsorption and reaction (SILAR) or electrodeposition, with an aim towards tuning the photoelectrochemical cell to the visible region. The PbS modification of the TiO(2) NTAs results in an increase in the visible light adsorption, however the increase in photocurrent is dependent on the modification method. PbS/TiO(2) NTAs prepared by SILAR and electrodeposition show, respectively, photocurrents of 11.02 and 5.72 mA/cm(2). The increase in photocurrent is attributed to enhanced charge separation efficiency and improved electron transport.     

Electrochemiluminescence cell fabrication using TiO2 nanotube produced by anodic oxidation

Electrochemiluminescence (ECL) cell using the electrode of TiO2 nanotube (NT) and Ru(ll) complex Ru(bpy)3(PF6)2 as a luminacence substance was fabricated. TiO2 NT were produced from the membrane of TiO2 NT arrays fabricated by anodic oxidation of approximately 100 microm thick Ti-plate. TiO2 NT arrays inject increasing number of electrons to the Ru(II) complex at the interface of TiO2 NTs. It allows the increasing exergonic oxidation/reduction reaction of Ru(II) complex. The ECL cell emits approximately 600 nm light in orange color. The cell structure is composed of a glass/F-doped SnO2(FTO)/TiO2 NT/Ru(II) complex in propylene carbonate/FTO/glass. The ECL efficiency of the cell consisting of the layer of TiO2 NT was approximately 255 cd/m2 at a bias of 4 V. The use of TiO2 NT increases ECL intensities by 5 times compared to the typical ECL cell without the use of TiO2 NT.     

Reduction of charge recombination by an amorphous titanium oxide interlayer in layered graphene/quantum dots photochemical cells

The effect of an amorphous TiO(x) interlayer on layered graphene/quantum dots photochemical cells has been investigated. The addition of the TiO(x) interlayer eliminates the decay of photocurrent in the initial seconds after light illumination and significantly increases the slope of the steady-state photocurrent versus the light intensity. The open-circuit voltage decay measurements further illustrate a longer electron lifetime when an amorphous TiO(x) interlayer is applied. Consequently, the photocurrent and photovoltage of the photovoltaic cell with a TiO(x) interlayer are greatly increased. This work demonstrates that the graphene/amorphous TiO(x) composite structure effectively inhibits charge recombination while enhancing charge transfer, providing a promising scaffold for quantum dots and dye-sensitized photovoltaic cells.     

Novel carbon-doped TiO2 nanotube arrays with high aspect ratios for efficient solar water splitting

The photocatalytic splitting of water into hydrogen and oxygen using solar light is a potentially clean and renewable source for hydrogen fuel.(1,2) There has been extensive investigation into metal-oxide semiconductors such as TiO(2), WO(3), and Fe(2)O(3), which can be used as photoanodes in thin-film form.(3-5) Of the materials being developed for photoanodes, TiO(2) remains one of the most promising because of its low cost, chemical inertness, and photostability.(6) However, the widespread technological use of TiO(2) is hindered by its low utilization of solar energy in the visible region. In this study, we report the preparation of vertically grown carbon-doped TiO(2) (TiO(2-x)C(x)) nanotube arrays with high aspect ratios for maximizing the photocleavage of water under white-light irradiation. The synthesized TiO(2-x)C(x) nanotube arrays showed much higher photocurrent densities and more efficient water splitting under visible-light illumination (> 420 nm) than pure TiO(2) nanotube arrays. The total photocurrent was more than 20 times higher than that with a P-25 nanoparticulate film under white-light illumination.     

Photoelectrochemical detection of pentachlorophenol with a multiple hybrid CdSe(x)Te(1-x)/TiO2 nanotube structure-based label-free immunosensor

Driven by the urgent demand of detecting trace amounts of pentachlorophenol (PCP) in contaminative water, a label-free immunosensor with ultra sensitivity and high selectivity was constructed based on a hybrid CdSe(x)Te(1-x) (0 ≤ x ≤ 1) nanocrystal (NCs)-modified TiO(2) nanotube (NT) arrays for the first time. The CdSe(x)Te(1-x) NCs were photoelectrodeposited on inner and outer space of the TiO(2) NTs, leading to high photoelectrical conversion efficiency in the visible region. PCP antibodies are covalently conjugated on the TiO(2) NTs due to the large surface area and good biocompatibility. Since the photocurrent is highly dependent on the TiO(2) surface properties, the specific interaction between PCP and the antibodies results in a sensitive change in the photocurrent, with a limit of detection (LOD) of 1 pM. High sensor-to-sensor reproducibility is achieved. The sensor was applied for the direct analysis of river water samples.     

Fast fabrication of long TiO2 nanotube array with high photoelectrochemical property on flexible stainless steel

Oriented highly ordered long TiO2 nanotube array films with nanopore structure and high photoelectrochemical property were fabricated on flexible stainless steel substrate (50 microm) by anodization treatment of titanium thin films in a short time. The samples were characterized by means of field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and photoelectrochemical methods, respectively. The results showed that Ti films deposited at the condition of 0.7 Pa Ar pressure and 96 W sputtering power at room temperature was uniform and dense with good homogeneity and high crystallinity. The voltage and the anodization time both played significant roles in the formation of TiO2 nanopore-nanotube array film. The optimal voltage was 60 V and the anodization time is less than 30 min by anodizing Ti films in ethylene glycerol containing 0.5% (w) NH4F and 3% (w) H2O. The growth rate of TiO2 nanotube array was as high as 340 nm/min. Moreover, the photocurrent-potential curves, photocurrent response curves and electrochemical impedance spectra results indicated that the TiO2 nanotube array film with the nanoporous structure exhibited a better photo-response ability and photoelectrochemical performance than the ordinary TiO2 nanotube array film. The reason is that the nanoporous structure on the surface of the nanotube array can separate the photo electron-hole pairs more efficiently and completely than the tubular structure.     

Use of highly-ordered TiO(2) nanotube arrays in dye-sensitized solar cells

We describe the use of highly ordered transparent TiO(2) nanotube arrays in dye-sensitized solar cells (DSCs). Highly ordered nanotube arrays of 46-nm pore diameter, 17-nm wall thickness, and 360-nm length were grown perpendicular to a fluorine-doped tin oxide-coated glass substrate by anodic oxidation of a titanium thin film. After crystallization by an oxygen anneal, the nanotube arrays are treated with TiCl(4) to enhance the photogenerated current and then integrated into the DSC structure using a commercially available ruthenium-based dye. Although the negative electrode is only 360-nm-thick, under AM 1.5 illumination the generated photocurrent is 7.87 mA/cm(2), with a photocurrent efficiency of 2.9%. Voltage-decay measurements indicate that the highly ordered TiO(2) nanotube arrays, in comparison to nanoparticulate systems, have superior electron lifetimes and provide excellent pathways for electron percolation. Our results indicate that remarkable photoconversion efficiencies may be obtained, possibly to the ideal limit of approximately 31% for a single photosystem scheme, with an increase of the nanotube-array length to several micrometers.     

Enhanced charge-collection efficiencies and light scattering in dye-sensitized solar cells using oriented TiO2 nanotubes arrays

We report on the microstructure and dynamics of electron transport and recombination in dye-sensitized solar cells (DSSCs) incorporating oriented TiO2 nanotube (NT) arrays. The morphology of the NT arrays, which were prepared from electrochemically anodized Ti foils, were characterized by scanning and transmission electron microscopies. The arrays were found to consist of closely packed NTs, several micrometers in length, with typical wall thicknesses and intertube spacings of 8-10 nm and pore diameters of about 30 nm. The calcined material was fully crystalline with individual NTs consisting of about 30 nm sized crystallites. The transport and recombination properties of the NT and nanoparticle (NP) films used in DSSCs were studied by frequency-resolved modulated photocurrent/photovoltage spectroscopies. While both morphologies display comparable transport times, recombination was much slower in the NT films, indicating that the NT-based DSSCs have significantly higher charge-collection efficiencies than their NP-based counterparts. Dye molecules were shown to cover both the interior and exterior walls of the NTs. Analysis of photocurrent measurements indicates that the light-harvesting efficiencies of NT-based DSSCs were higher than those found for DSSCs incorporating NPs owing to stronger internal light-scattering effects.     

Hydrogen-treated TiO2 nanowire arrays for photoelectrochemical water splitting

We report the first demonstration of hydrogen treatment as a simple and effective strategy to fundamentally improve the performance of TiO(2) nanowires for photoelectrochemical (PEC) water splitting. Hydrogen-treated rutile TiO(2) (H:TiO(2)) nanowires were prepared by annealing the pristine TiO(2) nanowires in hydrogen atmosphere at various temperatures in a range of 200-550 °C. In comparison to pristine TiO(2) nanowires, H:TiO(2) samples show substantially enhanced photocurrent in the entire potential window. More importantly, H:TiO(2) samples have exceptionally low photocurrent saturation potentials of -0.6 V vs Ag/AgCl (0.4 V vs RHE), indicating very efficient charge separation and transportation. The optimized H:TiO(2) nanowire sample yields a photocurrent density of ～1.97 mA/cm(2) at -0.6 V vs Ag/AgCl, in 1 M NaOH solution under the illumination of simulated solar light (100 mW/cm(2) from 150 W xenon lamp coupled with an AM 1.5G filter). This photocurrent density corresponds to a solar-to-hydrogen (STH) efficiency of ～1.63%. After eliminating the discrepancy between the irradiance of the xenon lamp and solar light, by integrating the incident-photon-to-current-conversion efficiency (IPCE) spectrum of the H:TiO(2) nanowire sample with a standard AM 1.5G solar spectrum, the STH efficiency is calculated to be ～1.1%, which is the best value for a TiO(2) photoanode. IPCE analyses confirm the photocurrent enhancement is mainly due to the improved photoactivity of TiO(2) in the UV region. Hydrogen treatment increases the donor density of TiO(2) nanowires by 3 orders of magnitudes, via creating a high density of oxygen vacancies that serve as electron donors. Similar enhancements in photocurrent were also observed in anatase H:TiO(2) nanotubes. The capability of making highly photoactive H:TiO(2) nanowires and nanotubes opens up new opportunities in various areas, including PEC water splitting, dye-sensitized solar cells, and photocatalysis.     

P-type Cu--Ti--O nanotube arrays and their use in self-biased heterojunction photoelectrochemical diodes for hydrogen generation

Copper and titanium remain relatively plentiful in the earth's crust; hence, their use for large-scale solar energy conversion technologies is of significant interest. We describe fabrication of vertically oriented p-type Cu-Ti-O nanotube array films by anodization of copper rich (60% to 74%) Ti metal films cosputtered onto fluorine doped tin oxide (FTO) coated glass. Cu-Ti-O nanotube array films 1 mum thick exhibit external quantum efficiencies up to 11%, with a spectral photoresponse indicating that the complete visible spectrum, 380 to 885 nm, contributes significantly to the photocurrent generation. Water-splitting photoelectrochemical pn-junction diodes are fabricated using p-type Cu-Ti-O nanotube array films in combination with n-type TiO 2 nanotube array films. With the glass substrates oriented back-to-back, light is incident upon the UV absorbing n-TiO 2 side, with the visible light passing to the p-Cu-Ti-O side. In a manner analogous to photosynthesis, photocatalytic reactions are powered only by the incident light to generate fuel with oxygen evolved from the n-TiO 2 side of the diode and hydrogen from the p-Cu-Ti-O side. To date, we find under global AM 1.5 illumination that such photocorrosion-stable diodes generate a photocurrent of approximately 0.25 mA/cm (2), at a photoconversion efficiency of 0.30%.