Effect of different Bi/Ti molar ratios on visible-light photocatalytic activity of BiOI/TiO2 heterostructured nanofibers

In this study, bismuth oxyiodide/titanium dioxide (BiOI/TiO₂) heterostructures with different molar ratios of Bi and Ti were synthesized by electrospinning and hydrothermal methods. The samples thus synthesized were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy, and ultraviolet–visible diffuse reflectance spectroscopy. The results confirmed the presence of the BiOI/TiO₂ heterojunction with Bi/Ti molar ratios of 0.20–1 by electrospinning and hydrothermal methods. Photocatalytic activity was also evaluated by the degradation of methylene blue (MB) under visible-light irradiation. The 80% BiOI/TiO₂ heterostructure exhibited the best photocatalytic activity for the degradation of MB under visible-light irradiation.     

A simple and efficient method for the synthesis of SiBNC ceramics with different Si/B atomic ratios

The high-temperature durability of SiBNC ceramics is significantly influenced by Si/B ratios and the synthetic procedures. Single-source synthetic routes can yield homogeneous ceramics at the atomic level, but the Si/B ratio cannot be efficiently adjusted. In this paper, a simple and efficient method for the synthesis of SiBNC precursor polyborosilazanes (PBSZs) with different Si/B ratios has been established via a one-pot reaction involving boron trichloride, dichloromethylsilane and hexamethyldisilazane in different molar ratios. The Si/B ratios of the derived SiBNC ceramics were consistent with that of the precursor PBSZs. When pyrolysed at 1000 °C, PBSZs with 0.52, 0.94 and 2.12 Si/B ratios transformed into SiB_2.6N₅C_2.2, SiB_0.9N_2.7C_1.3 and Si₂BN₃C_1.4 ceramics respectively. The polymer-to-ceramic process was also studied and featured ceramic yields of 43.2 wt%, 50.1 wt% and 62.2 wt%, respectively. The derived ceramic SiB_0.9N_2.7C_1.3 resisted crystallization up until 1700 °C, whereas the SiB_2.6N₅C_2.2 and Si₂BN₃C_1.4 could remain amorphous up to 1600 °C only. Using the precursor with 0.94 Si/B ratio, the SiBNC ceramic fibres were also obtained.     

Effect of humidity on the photocatalytic degradation of trichloroethylene in gas Phase over TiO2 thin films treated by different conditions

The effect of humidity on the photocatalytic degradation reaction of trichloroethylene (TCE) in gas phase was investigated by using pretreated TiO₂ sol-gel films. It was observed that the photocatalytic activity of the TiO₂ films depended more greatly on the pretreatment conditions, for example, UV pre-illumination, than on the moisture content. When the relative humidity was over 50%, the reaction rates decreased regardless of treatment conditions of the photocatalyst. The photocatalytic decomposition rate of TCE increased with the increase of light intensity. However, the influence of humidity on the reaction rate was less significant under the increased light intensity. The intermediates and byproducts of the reaction were not changed in different humidity conditions.     

One step from nanofiber to functional hybrid structure: Pd doped ZnO/SnO2 heterojunction nanofibers with hexagonal ZnO columns for enhanced low-temperature hydrogen gas sensing

In this paper, a novel hybrid structure of Pd doped ZnO/SnO₂ heterojunction nanofibers with hexagonal ZnO columns was one step synthesized from electrospun precursor nanofibers. Due to the synergistic effect of hexagonal ZnO, SnO₂ and Pd, the structure exhibited excellent hydrogen (H₂) gas sensing properties. At low-temperature of 120 °C, the response (R_a/R_g) to 100 ppm H₂ gas exceeded 160, the response/recovery time was only 20 s and 6 s respectively and the limit of detection was only 0.5 ppm. Meanwhile, it also had good selectivity for H₂ gas and excellent linearity. In addition, the materials were characterized by XRD, FESEM, HRTEM, XPS, and the synthesis mechanism and gas sensing mechanism were proposed.     

A PFSA Composite Membrane with Sulfonic Acid Functionalized TiO2 Nanotubes for Polymer Electrolyte Fuel Cells and Water Electrolysers

Titanate nanotubes (TiO₂‐NT) were functionalized with sulfonic acid functional groups and characterized with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X‐ray diffraction (XRD). Results confirmed that sulfonic acid groups were grafted onto TiO₂‐NT with a uniform distribution. When the functionalized titanate nanotube (F‐TiO₂‐NT) was incorporated in perfluorosulfonic acid membranes, the membrane conductivity and water uptake were improved. Polymer electrolyte membrane (PEM) fuel cells using 5 wt.% F‐TiO₂‐NT incorporated composite membrane exhibited a peak power density of 429 mW cm^–2 with non‐humidified O₂ at 90 °C, which is about four times higher than that with Nafion 117 membrane at identical conditions. PEMWE with 5 wt.% F‐TiO₂‐NT incorporated composite membrane achieved 1,000 mA cm^–2 current density at voltages below 1.6 V at 90 °C without back pressurizing.     

TiO_2/SiO_2复合纳米纤维的GQDs改性及其对甲醛的可见光催化降解性能

采用静电纺丝法合成了TiO_2/SiO_2柔性复合纳米纤维膜,而后对其进行石墨烯量子点(GQDs)改性,制备了GQDs/TiO_2-SiO_2复合纳米纤维,其中GQDs用水热法合成。用X射线衍射仪(XRD)、电子万能材料试验机、扫描电子显微镜(SEM)、紫外-可见分光光度计(UV-Vis)对其物相组成、力学性能、微观形貌以及光催化性能进行了表征。结果表明:尺寸在7 nm~15 nm之间的GQDs松散沉积在直径为200 nm~400 nm的TiO_2/SiO_2纳米纤维上,纤维连续性好,复合薄膜有较好的力学性能;TiO_2的结晶较好,为锐钛矿相;GQDs复合后将TiO_2的本征吸收从390 nm左右延伸到了420 nm左右,拓宽了TiO_2的吸收范围。在可见光催化降解中,初始浓度为0.32 mg/m~3的甲醛气体110 min后的降解效率达到70%。     

A method for structural characterization of the range of cylindrical nanocarbons: Nanotubes to nanofibers

Given the wealth of carbon multi-walled carbon nanotubes (MWNTs) and nanofiber synthesis strategies and resulting forms, there is an increasing need to better classify these materials in terms of their nanostructure. Apart from distinguishing the different nanoforms, such classification may be particularly useful for relating MWNT or nanofiber performance within various applications to their nanostructure. Demonstrated here is the use of image analysis algorithms applied to high resolution transmission electron microscopy (HRTEM) images of MWNTs and nanofibers. The analysis of the HRTEM images allowed for four separate measurements to quantify the graphitic content of the nanotube and nanofiber samples. Each measurement was based upon the features of individual carbon layer plane segments, which appear as fringes in HRTEM images. These measures included fringe length, separation, tortuosity and orientation. Distributions in the form of histograms serve to quantify data contained in the HRTEM images as represented by these parameters. Such information can serve as a measure of the physical characteristics and resulting chemical and mechanical properties of the nanotubes, nanofibers and their utility in applications.     

不同硅铝比β分子筛的催化裂化性能对比

以大庆减压蜡油掺杂30%减压渣油为原料,在固定流化床评价装置上考察不同硅铝比的β分子筛助剂的催化裂化反应性能。结果表明,β分子筛硅铝比较小时,重油产率减小,轻油收率和总液体收率增加,气体（干气+液化气）产率减少,而汽油辛烷值增加,但过高硅铝比的β分子筛影响重油转化,适中硅铝比β分子筛助剂的反应性能较好。以中国石油天然气股份有限公司大连石化分公司四催化原料油为原料,在ACE装置上对比评价了直接合成与脱铝改性后获得的相近硅铝比的β分子筛助剂的催化裂化反应性能。结果表明,脱铝改性后获得的β分子筛的重油产率较低,轻油收率和总液体收率均有提高。     

TiO2光催化氧化降解偶氮染料废水的研究

以偶氮染料直接耐酸大红4BS模拟废水为研究对象,以TiO2为光催化剂,紫外灯作光源（80W）,探究了不同TiO2催化剂的用量、光照时间、溶液初始pH值及废水初始质量浓度等因素对偶氮染料废水降解率的影响。实验结果表明,偶氮染料直接耐酸大红4BS废水的最佳处理条件为：TiO2催化剂质量浓度1．2g／L,光照时间120min,初始pH值10,废水初始质量浓度20mg／L。在最佳处理条件下,对某染料厂的实际工业废水样进行了降解率的测定,得出其降解率在90％以上。     

纳米TiO2光催化法处理炼油废水的研究

采用纳米TiO2光催化技术对炼油废水中COD和NH3-N进行了降解试验研究,结果表明,pH值在7～8时,纳米TiO2光催化剂的最佳用量为2.5 g/L、COD和NH3-N的最佳光照时间为4 h时和2 h时,在废水CODCr、NH3-N的质量浓度分别为1 470、91 mg/L时,处理后分别下降到700、40 mg/L左右,COD和NH3-N的降解率分别达到50.1%和55%.     

Construction of metallic nanocrystalline TaB2 coupled with TiO2 for enhanced photocatalytic degradation

The search for new low-cost co-catalysts that can replace precious metals is highly desirable and challenging. Transition metal diboride can be ideal candidates due to their excellent electrical conductivity and suitable work function. In this work, a novel TaB₂@TiO₂ heterostructure has been successfully constructed by a facile sol-gel method. The results show that TaB₂ has a suitable work function and B–O bonds are formed at the interface of the TaB₂@TiO₂ heterojunction, which makes it easier for the photogenerated electrons of TiO₂ to migrate to the surface of TaB₂ and promotes the effective separation of photogenerated carriers. In addition, the metallic nanocrystalline TaB₂ also significantly increases the specific surface area of the heterojunction. The above two points lead to more hydroxyl radicals and superoxide radicals production, thus substantially improving the photocatalytic degradation performance. Therefore, the 3 wt% TaB₂ (TT3) catalyst degraded rhodamine B (RhB, 20 mg/L) with an efficiency of 100% under 90 min irradiation, which is much higher than pristine TiO₂～92% and commercial TiO₂ (P25)～64%. Furthermore, its photocatalytic rate is about 1.73 times and 3.77 times of pristine TiO₂ and commercial TiO₂ (P25), respectively. This finding can provide new insights for the replacement of photocatalytic noble metal co-catalysts.     

CuO/TiO2纳米纤维可见光催化CO2合成甲醇

以介孔SiO_2球为模板、TiCl4为前驱体,采用气相生长法制备了直径为8～10nm的TiO_2纳米纤维,然后采用浸渍法制备了具有异质结结构的CuO/TiO_2纳米纤维,在可见光照射下催化CO_2合成甲醇。通过SEM、TEM、XPS、UV-Vis、XRD、荧光光谱(PL)对催化剂进行了表征。结果表明:TiO_2纳米纤维较锐钛矿TiO_2纳米颗粒和商业TiO_2纳米颗粒(P25)荧光强度明显降低,光生电子-空穴对更加稳定。通过在TiO_2纳米纤维上负载CuO形成异质结结构后,进一步降低了催化剂的荧光强度,也增强了在可见光区的吸收。在300 W氙灯照射5 h进行光催化CO_2合成甲醇实验中,P25负载CuO后,催化合成甲醇产量为676μmol/g-cat,而负载了CuO的TiO_2纳米纤维,甲醇产量达1791μmol/g-cat,较CuO/P25提高了165%。     

New La3+ doped TiO2 nanofibers for photocatalytic degradation of organic pollutants: Effects of thermal treatment and doping loadings

The pure TiO₂ and lanthanum (La³⁺)-doped titanium dioxide (TiO₂) nanofibers were synthesized by electrospinning method followed via calcination at different temperatures (from 400 °C to 700 °C). Structures of the nanofibers were characterized by X-ray diffraction, scanning electron microscopy, TEM images and diffuse reflectance spectroscopy. The size of the nanofiber diameters was determined to be 129 and 101 nm, for pure TiO₂ and (0.1%)La³⁺:TiO₂ materials, respectively. The prepared nanofibers possess a crystalline structure, and wide distribution of the band-gaps, in the 2.867–3.210 eV range. Effects of La³⁺-dopant content, calcination temperature, and different doses of photocatalysts on the photodegradation efficiency were studied. The optimal level of La³⁺ and the optimal temperature of calcination were 0.1% La³⁺ and 600 °C, respectively. The photocatalytic degradation of methylene blue (91%, with a rate constant of 2.179 × 10^?2 min^?1) and ciprofloxacin (CIP) (99.5%, with a rate constant of 1.981 × 10^?2 min^?1) pollutants was highest on the (0.1%)La³⁺:TiO₂ annealed at 600 °C, after 300 min irradiation under visible light. This photocatalyst displayed sustainable efficiency for CIP degradation up to five consecutive uses.     

New strategy of photodynamic treatment of TiO2 nanofibers combined with celastrol for HepG2 proliferation in vitro

As one of the best biocompatible semiconductor nanomaterials, TiO(2) nanofibers can act as a good photosensitizer material and show potential application in the field of drug carriers and photodynamic therapy to cure diseases. Celastrol, one of the active components extracted from T. wilfordii Hook F., was widely used in traditional Chinese medicine for many diseases. In this study, the cytotoxicity of celastrol for HepG2 cancer cells was firstly explored. The results showed that celastrol could inhibit cancer cell proliferation in a time-dependent and dose-dependent manner, inducing apoptosis and cell cycle arrest at G2/M phase in HepG2 cells. After the TiO(2) nanofibers were introduced into the system of celastrol, the cooperation effect showed that the nanocomposites between TiO(2) nanofibers and celastrol could enhance the cytotoxicity of celastrol for HepG2 cells and cut down the drug consumption so as to reduce the side-effect of the related drug. Associated with the photodynamic effect, it is evident that TiO(2) nanofibers could readily facilitate the potential application of the active compounds from natural products like celastrol. Turning to the advantages of nanotechnology, the combination of nanomaterials with the related monomer active compounds of promising Chinese medicine could play an important role to explore the relevant mechanism of the drug cellular interaction and promote the potential application of TiO(2) nanofibers in the clinical treatment.     

基于静电纺丝技术制备Cu2+掺杂TiO2纳米纤维的研究

以聚苯乙烯溶液为络合剂与钛酸丁脂/醋酸铜混合制得前驱体,采用静电纺丝法制得聚苯乙烯(PS)/钛酸丁脂[Ti(OC4H9)4]/醋酸铜[Cu(CH3COO)2·H2O]复合纤维,经焙烧后得到均一直径、具有较高比表面积和多孔结构的TiO2/CuO复合纳米纤维.对所制得的纳米纤维的结晶度、表面形貌,分别采用X射线粉末衍射、红外光谱( IR) 、扫描电镜(SEM) 等分析测试手段进行了表征.结果表明,煅烧温度、PS浓度、钛酸丁脂浓度对纤维的直径和形貌有很大影响.     

活性炭纤维负载TiO2光催化降解甲醛研究

用浸渍-提拉法将TiO₂负载到活性炭纤维(ACF)上,在254 nm的紫外光源下,利用复合材料进行吸附光催化氧化甲醛气体动态实验研究。结果表明,甲醛的降解率随进口气量的增加有所下降;随TiO₂负载质量分数的增加,复合材料的比表面积由830 m²·g^-1降低到128.31 m²·g^-1;反应温度升高,去除率下降;当湿度小于40%时,随着湿度的增加,甲醛去除率增大;湿度继续增加时,光催化反应速率反而降低;活性炭负载TiO2光催化降解甲醛过程长时间使用会产生催化剂失活。     

TiO2纳米管阵列电催化降解甲基橙

采用阳极氧化法制备了TiO2纳米管阵列电极,通过考察其对模拟染料废水甲基橙(MO)的光催化降解效率来优化制备条件。研究了TiO2纳米管阵列电极电催化降解MO的活性及其影响因素,并考察了MO降解反应动力学。结果表明,MO溶液pH、电解槽压、支持电解质浓度等是TiO2纳米管阵列电极催化效率的重要影响因素。TiO2纳米管阵列电催化降解MO的反应遵守一级反应动力学规律,与TiO2纳米管阵列光催化降解MO的行为一致,且表观反应速率常数不随MO溶液浓度不同而发生改变。     

Surface chemical structures of CoO x /TiO2 catalysts for continuous wet trichloroethylene oxidation

An earlier sample of 5% CoO _x /TiO₂ used for the wet oxidation of TCE at 310 K forca. 6 h has been characterized with a fresh catalystvia XRD and XPS measurements. The binding energy for Co 2p_3/2 of the fresh sample appeared at 781.3 eV, which was very similar to the chemical states of CoTiO _x such as Co₂TiO₄ and CoTiO₃, whereas the spent catalyst indicated a 780.3-eV main peak for Co 2p_3/2 with a satellite structure at a higher energy region. This binding energy was almost equal to that of Co₃O₄ among reference Co compounds used. The phase structure of Co₃O₄ was revealed upon XRD measurements for all the catalyst samples. Based on these XPS and XRD results, a surface chemical structure of CoO _x species existing with the fresh catalyst can be proposed to be predominantly Co₃O₄ encapsulated completely by very thin filmlike CoTiO _x consisting of Co₂TiO₄ and/or CoTiO₃, with a tiny amount of Co₃O₄ particles covered partially by such cobalt titanates which may be responsible to the initial catalytic activity. Those CoTiO _x overlayers on Co₃O₄ particles may be readily removed into the wet media within 1 h at 310 K based on our earlier study, thereby giving rapid increase in the catalytic activity for that period.     

添加TiO2的聚合物电解质膜PVDF-HFP的性能研究

通过添加不同质量分数的TiO2纳米粒子制备多孔聚合物电解质膜PVDF-HFP,制备的聚合物电解质膜通过红外,交流阻抗,线性伏安扫描、首次充放电测试等方法进行了性能测试。添加TiO2纳米填料后,降低了聚合物链的结晶度和极性,当填料的质量分数为8%时,表现出较好的电化学性能,吸液率为184%,孔隙率为93%,室温电导率达到2.05×10-3 S/cm,电化学稳定窗口为4.7V,能满足要求。     

A different chemical route to prepare hafnium diboride-based nanofibers: Effect of chemical composition

This study reports on the synthesis of hafnium diboride (HfB₂)-based nanofibers via electrospinning of polyhafnoxanesal (PHO)-based solution followed by pyrolyzing hafnium-boron containing polyvinylpyrrolidone precursor fibers by a moderate heat treatment at 1500°C under argon atmosphere. The influence of the molar ratios of C/Hf and B/Hf in preceramic polymer method is investigated on the final phase of HfB₂-based nanofibers. Structural, thermal, microstructural, and physical properties of the hafnium-based fibers are evaluated using Fourier transform infrared spectra (FTIR), thermogravimetry and differential scanning calorimetry (TG/DSC), X-ray diffractometer (XRD), high-temperature X-ray diffraction (HT-XRD), field-emission scanning electron microscope/energy-dispersive spectrometer (FE-SEM/EDS), and Brunauer-Emmett-Teller (BET). The results unveiled that the acidic pH was the optimal condition needed for obtaining the single phase of HfB₂ nanofibers. The precursor fibers with the stoichiometric ratio of 1:4:5 of Hf:B:C prepared under the acidic conditions converted into pure HfB₂ nanofibers having rough and porous surface after pyrolysis at 1500°C for 2 hour in argon, whereas HfB₂-HfC composite nanofibers with smooth surface were produced in the neutral conditions. The HfB₂ nanofibers with a mean diameter of ~100 nm prepared under the acidic conditions showed a higher specific surface area compared to HfB₂-HfC composite nanofibers with a diameter of ~121 nm derived in the neutral conditions.