Preparation of TiO2/CNTs nanocomposite and its catalytic performance on the thermal decomposition of ammonium perchlorate

Transition Metal Chemistry - Composite particles of carbon nanotubes (CNTs) and titanium dioxide (TiO2) were prepared by a sol-flux method. Characterization of TiO2/CNTs nanocomposite was performed...     

CNTs/TiO2多孔复合膜的组装及光催化性能

提出了一种在掺氟的SnO2(FTO)导电玻璃上组装碳纳米管(CNTs)/Fe-Ni/TiO2多孔复合膜光催化剂的新方法.采用喷涂热解法(SPD)将掺杂镍和铁的含有嵌段聚合物P123的二氧化钛前驱体溶胶涂覆在FTO导电玻璃上,制备Fe-Ni/TiO2多孔膜,再采用化学气相沉积法(CVD)在Fe-Ni/TiO2膜上原位生长CNTs,得到CNTs/Fe-Ni/TiO2多孔复合膜光催化剂.CNTs/Fe-Ni/TiO2复合膜具有多级孔结构特征,在TiO2表面原位生长的CNTs不但具有较好的石墨化结构,且CNTs较均匀地分布在整个膜层的孔中.考察了CNTs/Fe-Ni/TiO2复合膜光催化剂的结构和性能,并通过降解甲基橙溶液评价了复合膜的光催化活性.结果表明,CNTs的复合及铁和镍的掺杂等改性显著提高了TiO2膜材料的光催化活性.     

Enhanced visible-light activity of titania via confinement inside carbon nanotubes

Titania confined inside carbon nanotubes (CNTs) was synthesized using a restrained hydrolysis method. Raman spectra and magnetic measurements using a SQUID magnetometer suggested the formation of remarkable oxygen vacancies over the encapsulated TiO(2) in comparison with nanoparticles dispersed on the outer surface of CNTs, extending the photoresponse of TiO(2) from the UV to the visible-light region. The CNT-confined TiO(2) exhibited improved visible-light activity in the degradation of methylene blue (MB) relative to the outside titania and commercial P25, which is attributed to the modification of the electronic structure of TiO(2) induced by the unique confinement inside CNTs. These results provide further insight into the effect of confinement within CNTs, and the composites are expected to be promising for applications in visible-light photocatalysis.     

Enhanced photocatalytic activity of mesoporous TiO2 aggregates by embedding carbon nanotubes as electron-transfer channel

Mesoporous multiwalled carbon nanotubes/titanium dioxide (CNTs/TiO(2)) nanocomposites with low loading amounts (0-0.5 wt%) of CNTs embedded inside mesoporous TiO(2) aggregates has been prepared by a simple one-pot hydrothermal method using titanium sulfate as titanium source. The as-prepared CNTs/TiO(2) samples are carefully characterized, analyzed and discussed. In contrast to previous reports with high CNT loading, our results indicate that a low CNT loading slightly influences the textural properties (including crystallite size, degree of crystallinity, specific surface areas, and pore volume etc.) and UV-light absorption of the mesoporous TiO(2) aggregates. The SEM and TEM results demonstrate that the CNTs are mostly embedded in the mesoporous TiO(2) aggregates. Moreover, chemical bonds are formed at the interface between CNTs and TiO(2), which is confirmed by the Raman, IR and XPS analyses. Significantly, we point out that PL analysis in terms of intensity of PL signals seems to not be a reliable way to monitor the recombination rate in the CNTs/TiO(2) composite, due to the quenching effect of CNTs. Instead, the analysis of transient photocurrent responses is introduced, which definitely reflects CNTs as fast electron transfer channels in chemically-bonded CNTs/TiO(2) composites with low CNT loading. Notably, the positive synergy effects of CNTs and TiO(2) depend on both the CNT loading amount and the state of interfacial contacts. In our study, only these chemically bonded CNTs/TiO(2) nanocomposites with appropriate loading amounts (<0.1 wt%) favor the separation of photogenerated electron-hole pairs and decrease their recombination rate and thus display significantly enhanced photocatalytic activity for degrading acetone in air under UV irradiation, as compared with pristine TiO(2) counterparts and commercial P25 photocatalyst. In contrast, a high CNT loading (>0.1 wt%) results in a decrease in photocatalytic activity; a simple mechanical mixing of CNTs and TiO(2) without forming chemical bonds at the interface also results in inferior photocatalytic performance.     

Visible light assisted photocatalytic degradation of organic dyes on TiO2–CNT nanocomposites

Journal of Sol-Gel Science and Technology - Carbon nanotubes (CNTs) uniformly decorated with nano-anatase TiO2 particles corresponding to different TiO2–CNT weight ratios (up to 90&nbsp;%...     

Effective photocatalytic degradation of atrazine over titania-coated carbon nanotubes (CNTs) coupled with microwave energy

Microwave-assisted photocatalytic (MAPC) degradation of atrazine over nanotitania coated multiwalled carbon nanotubes (TiO(2)/MWCNTs) was investigated in this study. As a result, degradation efficiency of atrazine over TiO(2)/CNTs prepared by hydrothermal method was about 30% and 20% higher than that of titania P25 and anatase prepared hydrothermally in given time. The TiO(2)/CNTs composite samples were characterized by TGA-DSC, TEM, UV-vis DRS, XRD and BET, to explain the reason for efficient degradation and adsorption process of atrazine. Microwave thermal effect in this process was also investigated. Intermediates of degradation both in MAPC process and microwave-assisted photodegradation (MAPD) process were identified by LC/MS. It suggests that MWCNTs have special effects on atrazine degradation during MAPC process, like strong microwave absorption capability.     

Preparation of nanocomposites of metals, metal oxides, and carbon nanotubes via self-assembly

Carbon nanotubes (CNTs)-based composites have attracted significant research interest in recent years, owing to their important applications in various technological fields. In this investigation, we describe a general approach to make CNTs-based nanocomposites via self-assembly. The method allows one to prepare binary composites as well as complex systems such as ternary or even quaternary composites where nanoparticles of active phases (e.g., metals and metal oxides) are used as primary building blocks. Six different kinds of binary, ternary, and quaternary nanocomposites, TiO2/CNTs, Co3O4/CNTs, Au/CNTs, Au/TiO2/CNTs, TiO2/Co3O4/CNTs, and Co/CoO/Co3O4/CNTs, have been reported herein in order to draw common features for various assembly schemes. To understand the interconnectivity between the active phases and CNTs, we have devised a range of experiments and examined the resultant samples with many instrumental techniques. On the basis of this work, we demonstrate that highly complex inorganic-organic nanohybrids with good controls in particle shape, size, and distribution can be fabricated from presynthesized nanobuilding units. Concerning their workability, we further show that self-assembled TiO2/CNTs are sufficiently robust and the electrochemical performance of TiO2 is significantly enhanced when it is used as a cathode material in Li-battery application.     

Reversible storage of molecular hydrogen by sorption into multilayered TiO2 nanotubes

The sorption of hydrogen between the layers of the multilayered wall of nanotubular TiO2 was studied in the temperature range of -195 to 200 degrees C and at pressures of 0 to 6 bar. Hydrogen can intercalate between layers in the walls of TiO2 nanotubes forming host-guest compounds TiO2 x xH2, where x < or = 1.5 and decreases at higher temperatures. The rate of hydrogen incorporation increases with temperature and the characteristic time for hydrogen sorption in TiO2 nanotubes is several hours at 100 degrees C. The rate of intercalate formation is limited by the diffusion of molecular hydrogen inside the multilayered walls of the TiO2 nanotube. 1H NMR-MAS and XRD data confirm the incorporation of hydrogen between the layers in the walls of TiO2 nanotubes. The nature and possible applications of the observed intercalates are considered.     

SiW12、PbS对提高TiO2纳米管光电转换效率的协同效应研究

复合薄膜可以改善TiO2纳米管在光电转换时电子-空穴易复合和吸收光谱范围窄的缺陷。用电沉积法将多酸H4SiW12O40（SiW12）沉积在TiO2纳米管表面形成SiW12/TiO2纳米管复合薄膜,再用连续离子层吸附反应法（SILAR）将PbS吸附到SiW12 /TiO2纳米管复合薄膜表面,形成PbS/ SiW12/TiO2纳米管复合薄膜,所得薄膜的光电转换效率相较于TiO2纳米管提高了57倍。X射线衍射（XRD）和扫描电子显微镜（SEM）表征结果表明,用电沉积法和连续离子层吸附反应法实现了PbS/SiW12/TiO2纳米管复合薄膜的制备;紫外可见（UV-vis）吸收光谱测试表明,复合薄膜的光吸收带边扩展到了可见光区域,电化学阻抗测试（EIS）表明,复合薄膜具有更高的电子转移速率;荧光光谱（PL）测试表明,复合薄膜拥有更小的电子-空穴复合率。以上结果说明,SiW12、PbS与TiO2纳米管复合,很好地抑制了TiO2纳米管电子-空穴的复合,并拓宽了吸收光谱范围,能显著地提高TiO2纳米管的光电性能。本文探索了一种有效提高TiO2纳米管光电转换效率的方法,对TiO2纳米管复合薄膜的制备具有一定的参考意义。     

TiO_2纳米管阵列的制备及其对316不锈钢光生阴极保护作用的研究

应用直接电化学阳极氧化法,于含氟电解液中,在纯钛表面制备一层整齐有序的TiO2纳米管阵列.扫描电子显微镜(SEM),X射线衍射(XRD)表征该纳米管阵列的形貌及晶体结构,光电化学联用系统研究其光电响应特性及对316L的光生阴极保护作用.结果表明:以TiO2纳米管阵列膜作为光生阳极时,在紫外光区(λ<387nm)有显著增强的光生电流响应,并对316不锈钢有较好的光生阴极保护作用.暗态下,光生电极电位仍可维持较长的一段时间,继续起到阴极保护作用.     

铁掺杂TiO2纳米管阵列对不锈钢的光生阴极保护

在含FeSO4的HF、H2SO4/HF、NaF/Na2SO4溶液中,通过电化学阳极氧化直接在纯钛表面制备Fe 掺杂的TiO2(Fe-TiO2)纳米管阵列. 应用X射线衍射(XRD)、扫描电子显微镜(SEM)、紫外-可见吸收光谱(UV-Vis)、X 射线光电子能谱(XPS)等手段对纳米管阵列的结构、形貌及化学组成进行表征. 利用光电化学测量研究Fe-TiO2纳米管阵列在不同波长范围内的光电响应特性和光生阴极保护行为. 考察了温度、时间、掺杂含量等参数对TiO2纳米管阵列的几何尺寸、形貌和光电性能的影响. 结果表明, Fe掺杂可有效减缓TiO2纳米管阵列载流子的复合, 窄化TiO2带隙宽度, Fe-TiO2在410-650 nm范围显示强吸收, 并使光谱响应扩展到波长大于400 nm 的可见光区. 实验结果还表明, Fe-TiO2纳米管阵列对316不锈钢(316L)具有良好的光生阴极保护作用, 暗态下阴极保护作用可继续维持.     

Alignment-retainable nitrogenation of cylindrical carbon nanotubes by thermal reaction with ammonia following UV oxidation: chemical alteration effects on electrical conductivity

Cylindrical carbon nanotubes (CNTs) pretreated by UV irradiation were able to react with NH(3) to give nitrogen-containing CNTs without destroying their vertically aligned morphology. This process provided incorporation of nitrogen mostly at pyridinic and pyrrolic sites and promoted disordering, which was correlated with decreased electrical conductivity of CNT yarns.     

Fixed-bed column studies of pentachlorophenol removal by use of alginate-encapsulated pillared clay microbeads

The high rate of electron/hole pair recombination reduces the quantum yield of the processes with TiO(2) and represents its major drawback. Adding a co-adsorbent increases the photocatalytic efficiency of TiO(2). In order to hybridize the photocatalytic activity of TiO(2) with the adsorptivity of carbon nanotube, a composite of multi-walled carbon nanotubes and titanium dioxide (MWCNT/TiO(2)) has been synthesized. The composite was characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared absorption spectroscopy (FTIR), and diffuse reflectance UV-vis spectroscopy. The catalytic activity of this composite material was investigated by application of the composite for the degradation of methyl orange. It was observed that the composite exhibits enhanced photocatalytic activity compared with TiO(2). The enhancement in photocatalytic performance of the MWCNT/TiO(2) composite is explained in terms of recombination of photogenerated electron-hole pairs. In addition, MWCNT acts as a dispersing agent preventing TiO(2) from agglomerating activity during the catalytic process, providing a high catalytically active surface area. This work adds to the global discussion of how CNTs can enhance the efficiency of catalysts.     

形状记忆聚偏氟乙烯/丙烯酸酯/碳纳米管纳米复合材料的导电及导热性能

利用聚偏氟乙烯（PVDF）微小结晶的物理交联点作用,制备了形状记忆性能优异的聚偏氟乙烯/丙烯酸酯聚合物（PVDF/ACM）共混材料,为提高其导电及导热性能,于其中引入了碳纳米管（CNT）,系统研究了PVDF/ACM/CNT三元体系纳米复合材料的导热及导电性能。 结果表明,碳纳米管在PVDF/ACM体系中分散均匀;在基本保持其形状记忆性能的前提下,碳纳米管的加入使材料导热性能及导电性能有较大程度的提高：质量分数为4%的CNT使材料25 ℃的电阻值降低至5000 Ω/square,导热系数提高至0.157 W/(m·K)。     

Accumulation of Electrolytic Hydrogen by Carbon Nanotubes

The accumulation of electrolytic hydrogen synthesized in a 5 M KOH solution by double- and triple-walled carbon nanotubes (CNTs) deposited on a steel membrane and encapsulated by an electrolytic iron layer of the thickness of 10 nm was studied. CNTs were synthesized by catalytic pyrolysis of methane and are characterized by an inner diameter of 2–4 nm, a length of up to 10 μm and more, and a specific surface area of 600–800 m² g^–1. The studies were performed by electrochemical diffusion, cyclic voltamperometry, and electrochemical-impedance spectroscopy. It has been shown that the hydrogen-storage capacity in CNTs varies in the range of 4–25% depending on the content of nanotubes in the composite.     

Surface-assisted laser desorption-ionization mass spectrometry on titanium dioxide (TiO2) nanotube layers

The paper reports on the use of a titanium oxide (TiO(2)) nanotube layer as a sensitive substrate for surface-assisted laser desorption-ionization mass spectrometry (SALDI-MS) of peptides and small molecules. The nanotube layers were prepared by electrochemical anodization of titanium foil. The optimized TiO(2) nanotubes morphology coupled to a controlled surface chemistry allowed desorption-ionization (D/I) of a peptide mixture (Mix1) with a detection limit of 10 femtomoles for the neurotensin peptide. The performance of the TiO(2) nanotubes for the D/I of small molecules was also tested for the detection of sutent, a small tyrosine kinase inhibitor, and verapamil. A detection limit of 50 fmol was obtained for these molecules, as compared to 500 fmol using classical matrix-assisted laser desorption-ionization mass spectrometry (MALDI-MS). Both amorphous and anatase TiO(2) layers displayed a comparable performance for D/I of analyte molecules. In a control experiment, we have performed D/I of analyte molecules on a flat TiO(2) layer. The absence of signal emphasizes the role of the nanostructured substrate in the D/I process.     

Flame retardancy of epoxy resin nanocomposite with a novel polymeric nanoflame retardant

A wrapped nanoflame retardant, designated as polyhedral oligomeric silsesquioxane (POSS)‐poly(4‐bromostyrene) (PBS)‐carbon nanotubes (CNTs), was synthesized via π‐π stacking interactions between the walls of multiwalled carbon nanotubes and the silicon‐bromine containing hybrid copolymer (designated as POSS‐PBS) that was copolymerized by 4‐bromostyrene and acryloyloxyisobutyl polyhedral oligomeric silsesquioxane. The POSS‐PBS‐CNTs exhibited good dispersibility in epoxy resin (EP) without obvious aggregation. Furthermore, the fire behaviors of this flame‐retardant EP (FR‐EP) nanocomposites were examined via limited oxygen index (LOI) and cone calorimeter (CONE) tests. The FR‐EP had an ideal LOI value of 35.3% and its residual char yield obtained from CONE test was significantly enhanced from 5.9% to 15.3% with the incorporation of 4 wt% POSS‐PBS‐CNTs and 1.33 wt% Sb₂O₃ into EP matrix. Additionally, the addition of 4 wt% POSS‐PBS‐CNTs or POSS‐PBS can efficiently decrease the peak heat release rate (PHRR) of EP matrix by 41.0% or 45.6%, respectively.     

多酸修饰二氧化钛纳米管复合膜的制备、表征及其光催化降解甲基橙的研究

采用电沉积方法制备了H3PW12O40(PW12)-TiO2复合膜,通过SEM,EDX和XRD等手段,对其组成和结构进行了表征,并考察了该复合膜催化剂对降解甲基橙的催化活性.实验结果表明PW12存在于TiO2纳米管结构中,用PW12多酸修饰的TiO2纳米管比单独的TiO2纳米管展示出更好的光催化性能,由于电子能够从TiO2纳米管导带转移到多酸的LUMO能级,有效抑制了光生电子和空穴的复合,因而使PW12-TiO2复合膜表现出更高的光催化活性.     

紫外光照射下 Fe-碳纳米管/TiO2 复合材料降解罗丹明 B

 The composites comprising Fe-carbon nanotubes (CNTs) on TiO2 were prepared by a modified sol-gel method and characterized by nitrogen adsorption, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and energy dispersive X-ray analysis. The photocatalytic decomposition of rhodamine B (Rh.B) under UV irradiation and air aeration catalyzed by the composites was measured. The photocatalytic activity of TiO2 nanoparticles was significantly enhanced by the large CNT network that facilitated electron transfer between adsorbed Rh.B molecules and the catalyst substrate and the simultaneous occurrence of the photo-Fenton reaction in the presence of Fe particles. A marked acceleration of the decomposition rate was observed with aeration by flowing air aeration due to the formation of the circulatory photo-Fenton system. Chemical oxygen demand of piggery waste was measured at regular intervals to evaluate the mineralization of wastewater.     

酞菁裂解法多壁碳纳米管的制备、表征和应用

In order to investigate the catalytic activity of high temperature treated CoPc toward oxygen reduction, and find the active site of the catalyst, using cobalt (Ⅱ) phthalocyanine (CoPc) as raw material, through thermal chemical vapor deposition method at 850℃ under a current of Ar/H2, two layer well-aligned multiwalled carbon nanotubes (CNTs) were made. The diameters of the well-aligned carbon nanotubes were distributed in the range of 60～120 nm and the length was about 40 μm. The Co particle with 10 nm in diameter was encapsulated in the CNTs compartment. The products were observed by field emission scanning electron microscope (SEM), and transmission electron microscope (TEM). The well-aligned carbon nanotubes were characteriszed by Raman scattering spectrum and X-ray diffraction (XRD). The cyclic voltammetric measurement demonstrates that the CNTs have some effect to prevent the metal nanoparticle encapsulated from eroding rapidly. It is assumed that the small amount of the N element in the CNTs is very necessary for the bamboo-like morphology and the protected action for metal particles against dissolution in the acid medium. The radian of the winding wall should be affected by the amount of the N and the interaction between the N in the carbon network and the metal cluster. In addition, the CNTs greater electrochemically active surface area is a great advantage for any electrocatalytic application.