CdS/TiO2纳米管复合结构的制备与光电性能研究

利用阳极氧化法在钛金属基体表面制备一层TiO₂纳米管阵列薄膜, 然后通过水热反应在TiO₂纳米管上负载CdS纳米粒子, 形成CdS/TiO₂纳米管的复合结构。利用SEM、XRD、XPS、UV-Vis等手段对其形貌和结构进行表征。进一步考察了CdS/TiO₂纳米管的光电性能和光催化活性, 结果表明, 相比于TiO₂纳米管, CdS/TiO₂纳米管复合结构在紫外光和可见光下都具有更好的光催化活性及光电性能。     

阳极氧化法制备二氧化钛纳米管及其在太阳能电池中的应用

介绍了阳极氧化法制备二氧化钛纳米管的技术发展历程, 论述了其制备过程及生长机理, 探讨了电解液、pH值、氧化电压、氧化时间、氧化温度和后处理方法等因素对TiO₂纳米管结构和形态的影响, 综述了近几年来利用TiO₂纳米管组装染料敏化、量子点和本体异质结等太阳能电池所取得的进展, 展望了其未来发展趋势和应用前景.     

阳极氧化法制备二氧化钛纳米管及其荧光性质

室温下采用电化学阳极氧化法在NaF、Na₂SO₄和H₂SO₄的混合溶液中用化学处理后的纯Ti片表面组装了一层结构高度有序的高密度TiO₂纳米管阵列。考察了几种主要的实验参数(阳极氧化电压、温度、电解液浓度)对TiO₂纳米管阵列形貌和尺寸的影响，探讨了二次阳极氧化对纳米管形貌的改善。对TiO₂纳米管阵列进行扫描电子显微镜(SEM)和荧光(PL)分析，探讨其生长机理。结果表明，孔径随阳极氧化电压的升高而变大，温度、电解液浓度影响反应过程中电流密度的大小；二次阳极氧化得到的纳米管的有序性有所改善，孔径大小更为均一，并且发现TiO₂纳米管的荧光具有量子效应。     

Fe2O3/TiO2纳米管阵列的制备及其光催化性能

在钛基体上采用阳极氧化法制备了TiO₂纳米管阵列,采用化学浴方法在TiO₂纳米管阵列上修饰了Fe₂O₃纳米颗粒.利用扫描电镜、X射线衍射和紫外可见漫反射光谱等手段对材料进行了表征,同时测试了材料的光电化学性能及其光催化降解亚甲基蓝染料废水的性能.结果表明,Fe₂O₃纳米颗粒的修饰将TiO₂纳米管阵列的光响应拓宽至可见光区域,提高了光电流,Fe₂O₃/TiO₂纳米管阵列的光电流是未修饰的TiO₂纳米管阵列的9倍.而在光催化反应中,亚甲基蓝最高降解率可达80%,比未修饰的TiO₂纳米管阵列高出30%.     

TiO2-MoO3复合纳米管阵列薄膜的制备及其可见光活性

通过阳极氧化的方法制备TiO₂纳米管薄膜, 在MoO₃存在的条件下对该薄膜进行热处理得到TiO₂-MoO₃复合纳米管阵列薄膜. 利用X射线衍射(XRD), 扫描电子显微镜(SEM), X射线光电子能谱(XPS), 电化学阻抗谱(EIS), Mott-Schottky 及光电化学方法对得到的薄膜进行了表征. XRD结果表明, TiO₂-MoO₃复合纳米管薄膜中的TiO₂主要为锐钛矿晶型. SEM实验证实了薄膜纳米管结构的存在, 样品中的MoO₃均匀地分散在TiO₂纳米管表面. 利用XPS方法分析了TiO₂-MoO₃复合纳米管薄膜元素的组成, 结果表明, MoO₃在TiO₂表面形成TiO₂-MoO₃复合纳米管薄膜. 研究了热处理温度以及热处理时间对样品的光电化学性能的影响, 相对于单纯TiO₂纳米管薄膜, 适量引入MoO₃提高了样品在可见光区的光电响应能力, 样品的平带电位负移. 在450 °C热处理60 min制得的TiO₂-MoO₃复合半导体纳米管阵列薄膜光电响应活性最高.     

热处理气氛对 TiO2 纳米管阵列薄膜光电催化性能的影响

 采用原位阳极氧化法在 Ti 基底上制备了高度有序的 TiO₂ 纳米管阵列薄膜, 分别在 O₂, 空气, Ar 和 H₂ 气氛中于 500 oC 进行结晶热处理, 考察了热处理气氛对 TiO₂ 纳米管阵列薄膜光电催化降解亚甲基蓝 (MB) 反应性能的影响. 结果表明, 在这些气氛中热处理得到的锐钛矿晶型的纳米管阵列薄膜对 MB 降解满足一级反应, 其速率常数分别为 4.967, 3.127, 1.989 和 1.625 h^-1 (0.5 V). 电化学阻抗分析表明, TiO₂ 纳米管的光电催化性能受控于光生电荷的传递特性. 在 O₂ 中热处理, TiO₂ 纳米管的光吸收及激发性能得以改善, 且电荷传递阻抗降低, 因而其光电催化性能最好.     

脉冲沉积制备Cu2O/TiO2纳米管异质结的可见光光催化性能

在用阳极氧化法制备有序排列TiO₂纳米管阵列薄膜的基础上,引入脉冲沉积工艺,成功实现了均匀、弥散分布的Cu₂O纳米颗粒修饰改性TiO₂纳米管阵列,形成Cu₂O/TiO₂ 纳米管异质结复合材料. 利用场发射扫描电镜（FESEM）、场发射透射电镜（FETEM）、X射线衍射（XRD）、X射线光电子能谱（XPS）和紫外-可见漫反射光谱（UV-Vis DRS）对样品进行表征,重点研究了Cu₂O/TiO₂ 纳米管异质结的光电化学特性和对甲基橙（MO）的可见光催化降解性能. 结果表明,Cu₂O纳米颗粒均匀附着在TiO₂纳米管阵列的管口和中部位置,所制备的Cu₂O/TiO₂ 纳米管异质结具有高效的可见光光催化性能;在浓度为0.01 mol·L^-1的CuSO₄溶液中制得的Cu₂O/TiO₂纳米管异质结表现出最好的电化学特性和光催化性能;另外,对Cu₂O纳米颗粒影响光催化活性的机理进行了讨论.     

TiO2-B纳米管负载过渡金属氧化物的电化学嵌锂性能

采用碱性条件下的水热法合成了质子钛酸盐纳米管,在此基础上采用化学沉淀方法制备了负载过渡金属(Co,Ni和Cu)氢氧化物的纳米管材料,然后在300 ℃氩气氛下烧结后得到负载过渡金属(Co,Ni和Cu)氧化物TiO₂-B纳米管。采用XRD和TEM等对其结构与形态进行了表征,采用恒电流充放电、循环伏安以及交流阻抗测试研究了其电化学嵌/脱锂性能。结果表明,TiO₂-B纳米管通过负载过渡金属(Co,Ni和Cu)氧化物纳米颗粒之后,改善了TiO₂-B纳米管的高倍率放电性能和循环稳定性。其中,负载NiO和CuO的TiO₂-B纳米管的高倍率放电性能和循环稳定性较为突出。研究还表明,负载过渡金属氧化物纳米颗粒后,有助于保持TiO₂-B纳米管在动态反应条件下的拟电容反应控制特征,并不同程度地减小了TiO₂-B纳米管的表面电荷转移电阻,这是TiO₂-B纳米管的电化学性能改善的主要原因。     

浸渍-分解法制备高可见光催化活性的Bi2O3/TiO2纳米管阵列

用浸渍-分解法将Bi₂O₃纳米颗粒沉积在TiO₂纳米管壁上, 制备了Bi₂O₃/TiO₂纳米管阵列. 用电感耦合等离子体发射光谱(ICP-AES)测定了Bi₂O₃/TiO₂ 纳米管阵列的化学组分, 利用X 射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和紫外-可见(UV-Vis)吸收光谱表征了所制备的样品. 通过在可见光下(λ>400 nm)降解甲基橙(MO)水溶液来评价样品的光催化活性. 结果表明, Bi₂O₃纳米颗粒均匀地沉积在TiO₂纳米管中. Bi₂O₃/TiO₂纳米管阵列具有比纯Bi₂O₃膜和N-TiO₂纳米管阵列高得多的可见光催化活性. Bi₂O₃/TiO₂纳米管阵列活性的增强是其强可见光吸收和Bi₂O₃与TiO₂之间形成的异质结的协同作用的结果.     

氟掺杂TiO2纳米管的可见光催化活性及第一性原理计算

作为光催化技术的核心, 提高TiO₂的光催化活性和对可见光的利用率是当前光催化研究中最重要的研究课题. 为了提高TiO₂纳米管的可见光催化活性, 采用化学气相沉积法对TiO₂纳米管进行了氟掺杂. 扫描电子显微镜(SEM)结果表明退火温度对于TiO₂纳米管的形貌完整性有较大影响, 当样品在550和700 °C下退火, 氟掺杂TiO₂纳米管结构受损; X射线衍射(XRD)分析表明氟掺杂对TiO₂由锐钛矿相转化为金红石相有阻碍作用; X射线光电子能谱(XPS)测试表明化学气相沉积能有效地对TiO₂纳米管进行非金属掺杂, 且该方法安全、操作简单. 氟掺杂TiO₂纳米管对甲基橙有较高的可见光催化降解活性. 第一性原理计算结果表明氟掺杂对TiO₂带隙无显著影响, 费米能级附近的F 2p轨道电子位于价带底部, 与O 2p交联作用较小, 因此对TiO₂光吸收带边影响不大. 氟掺杂能促进表面氧空穴的产生, 增加表面酸度与Ti³⁺, 有利于减少电子-空穴复合率, 从而提高其光催化活性.     

二氧化钛纳米管阵列的制备、改性及应用

二氧化钛因其在光催化、染料敏化太阳电池、生物医药等应用领域表现出优异性能而成为材料科学领域重点研究的化合物之一。本文介绍了近年来阳极氧化法制备不同形貌的TiO2纳米管(TiO2NTs)阵列,探讨了电解液、阳极氧化时间、电压三个因素对TiO2纳米管形貌的影响,综述了掺杂、复合、表面修饰这三种能对TiO2纳米管进行化学或物理修饰的改性手段以及改性后的TiO2纳米管阵列在光催化、太阳能电池、生物医学、传感等领域的应用研究进展。最后,指出国内外针对二氧化钛纳米管阵列研究现状所存在的问题,并对今后的研究工作提出了展望。     

TiO2 nanotubes: synthesis and applications

TiO(2) is one of the most studied compounds in materials science. Owing to some outstanding properties it is used for instance in photocatalysis, dye-sensitized solar cells, and biomedical devices. In 1999, first reports showed the feasibility to grow highly ordered arrays of TiO(2) nanotubes by a simple but optimized electrochemical anodization of a titanium metal sheet. This finding stimulated intense research activities that focused on growth, modification, properties, and applications of these one-dimensional nanostructures. This review attempts to cover all these aspects, including underlying principles and key functional features of TiO(2), in a comprehensive way and also indicates potential future directions of the field.     

Investigation on the dynamics of electron transport and recombination in TiO2 nanotube/nanoparticle composite electrodes for dye-sensitized solar cells

In this work, we report on fabrication and characterization of dye-sensitized solar cells based on TiO(2) nanotube/nanoparticle (NT/NP) composite electrodes. TiO(2) nanotubes were prepared by anodization of Ti foil in an organic electrolyte. The nanotubes were chemically separated from the foil, ground and added to a TiO(2) nanoparticle paste, from which composite NT/NP electrodes were fabricated. In the composite TiO(2) films the nanotubes existed in bundles with a length of a few micrometres. By optimizing the amount of NT in the paste, dye-sensitized solar cells with an efficiency of 5.6% were obtained, a 10% improvement in comparison to solar cells with pure NP electrodes. By increasing the fraction of NT in the electrode the current density increased by 20% (from 11.1 to 13.3 mA cm(-2)), but the open circuit voltage decreased from 0.78 to 0.73 V. Electron transport, lifetime and extraction studies were performed to investigate this behavior. A higher fraction of NT in the paste led to more and deeper traps in the resulting composite electrodes. Nevertheless, faster electron transport under short-circuit conditions was found with increased NT content, but the electron lifetime was not improved. The electron diffusion length calculated for short-circuit conditions was increased 3-fold in composite electrodes with an optimized NT fraction. The charge collection efficiency was more than 90% over a wide range of light intensities, leading to improved solar cell performance.     

Spatial arrangement of carbon nanotubes in TiO2 photoelectrodes to enhance the efficiency of dye-sensitized solar cells

Three electrode structures with different spatial arrangements of carbon nanotubes (CNTs) in the mesoporous TiO(2) layer were employed in dye-sensitized solar cells to study the effect of surface states at the interface formed by the incorporation of CNTs. It was found that the decay of open circuit voltage (V(oc)) was significantly minimized by avoiding the direct contact of nanotubes to the conducting substrate by introducing a thin buffer layer of TiO(2) while maintaining the superior electron collection efficiency from the incorporation of nanotubes.     

The preparation of highly ordered TiO2 nanotube arrays by an anodization method and their applications

The tubular-shaped nanostructure of TiO(2) is very interesting, and highly ordered arrays of TiO(2) nanotubes (TNTs) can be easily fabricated by anodization of the Ti substrate in specific electrolytes. Here in this feature article, we review synthesis methods for various TNTs including normal, alloy, and architectural forms such as bamboos, lace, and flowers. Specific nanosize architectures such as bamboo and lace types can be regulated by alternating voltage and further anodizing. In order to extend light response of TNTs to visible solar spectra, various dopings of specific elements have been discussed. The normal and modified TNTs are suggested for applications such as dye sensitized solar cells, water splitting, photocatalytic degradation of pollutants, CO(2) reduction, sensors, energy storage devices including Li ion batteries and supercapacitors, and other applications such as flexible substrate and biomaterials.     

Free-standing arrays of isolated TiO2 nanotubes through supercritical fluid drying

A common complication in fabricating arrays of TiO(2) nanotubes is that they agglomerate into tightly packed bundles during the inevitable solvent evaporation step. This problem is particularly acute for template-fabricated TiO(2) nanotubes, as the geometric tunability of this technique enables relatively large inter-pore spacings or, from another perspective, more space for lateral displacement. Our work showed that agglomeration results from the surface tension forces that are present as the ambient solvent is evaporated from the nanotube film. Herein, we report a processing and fabrication approach that utilizes supercritical fluid drying (CO(2)) to prepare arrays of template-fabricated TiO(2) nanotubes that are free-standing and spatially isolated. This approach could be beneficial to many emerging technologies, such as solid-state dye-sensitized solar cells and vertically-oriented carbon nanotube electrodes.     

TiO2 nanotube fabrication with highly exposed (001) facets for enhanced conversion efficiency of solar cells

We demonstrate that the use of poly(vinyl pyrrolidone) (PVP) and acetic acid during the synthesis of TiO(2) nanotubes may result in the synthesis of single-crystal-like anatase TiO(2) with a mainly exposed and chemically active (001) facet. An enhancement in the overall conversion efficiency of dye-sensitized solar cells was observed in a photoanode consisting of TiO(2) single-crystal-like anatase exposed (001) facets.     

Optimizing TiO(2) Nanotube Top Geometry for Use in Dye-Sensitized Solar Cells

Recombination dynamics: For TiO(2) nanotube-based dye-sensitized solar cells, the efficiency can be drastically enhanced by a synergetic effect that occurs when using nanowire-ended nanotubes in combination with an adequate nanoparticle decoration.     

Nb doping of TiO2 nanotubes for an enhanced efficiency of dye-sensitized solar cells

Nb-doped TiO(2) nanotube (with C(Nb) < 1 wt%) layers were successfully fabricated by self-ordered electrochemical anodization of Ti-Nb alloys. When used in dye-sensitized solar cells the efficiency enhanced by up to 30% compared to non-doped TiO(2) nanotubes. IMVS measurements indicate the beneficial effect to be due to lower recombination losses.