One-step Synthesis and Gas Sensing Properties of Hierarchical SnO2 Materials

Hierarchical tin oxide(SnO₂) architectures were synthesized with a facile hydrothermal method. In the hydrothermal synthesis, sodium dodecyl benzene sulfonate(SDBS) surfactant plays an important role as structure-directing reagent. The synthesized samples were characterized by powder X-ray diffraction(XRD), field emission scanning electron microscopy(FESEM), transmission electron microscopy(TEM) and high-resolution transmission electron microscopy(HRTEM). The results clearly reveal that the hierarchical architectures of SnO₂ were composed of aggregated nanosheets with a thickness of about 100 nm. A possible mechanism for the formation of the SnO₂ hierarchical architectures was proposed. In addition, the gas sensing properties of the as-prepared products were investigated and it was found that the sensor based on the special SnO₂ hierarchical architectures exhibited a high response and good selectivity to NO₂ at the optimal working temperature of 160 ℃.     

ZnO掺杂的SnO_2纳米纤维的制备、表征及气敏机理(英文)

以二水氯化亚锡(SnCl2·2H2O)为盐原料,采用静电纺丝的方法制备了SnO2纳米纤维.为了研究ZnO掺杂对SnO2形貌、结构及化学成分的影响,分别制备了不同含量ZnO掺杂的SnO2/ZnO复合材料.利用热重-差热分析(TG-DTA)、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱仪、扫描电镜(SEM)及能量色散X射线(EDX)光谱对材料的结晶学特性及微结构进行了表征.制备的SnO2/ZnO复合材料是由纳米量级的小颗粒构成的分级结构材料.ZnO含量不同,对应的SnO2/ZnO复合材料结构不同.表征结果表明ZnO的掺杂量对SnO2材料的形貌及结构均起着重要作用.将制备的不同ZnO含量的SnO2/ZnO复合材料进行气敏测试,测试结果表明,Sn:Zn摩尔比为1:1制作的气敏元件对甲醇的灵敏度优于其它摩尔比的气敏元件.讨论了SnO2/ZnO复合材料气敏元件的敏感机理.同时针对Sn:Zn摩尔比为1:1时表现出最好的气敏响应,分析了其原因,包括Zn的替位式掺杂行为、ZnO的催化作用、过量ZnO对SnO2生长的抑制作用以及SnO2与ZnO晶粒界面处的异质结.     

Effect of Nanoparticle Size on Gas-sensing Properties of Tin Dioxide Sensors

Sn(OH)₄ was prepared by the conventional solution precipitate method, followed by supercritical CO₂ drying. The resultant Sn(OH)₄ was divided into three aliquots and calcined at 400, 600 and 800℃, respectively, thus SnO₂ nanoparticles with average crystallite sizes of 5, 10 and 25 nm were obtained. Furthermore, three SnO₂ thick film gas sensors(denoted as sensors S-400, S-600 and S-800) were fabricated from the above SnO₂ nanoparticles. The adhesion of sensing materials on the surface of alumina tube is good. Compared to the sensors S-600 and S-800, sensor S-400 showed a much higher sensitivity to 1000 μL/L ethanol. On the other hand, sensor S-800 showed a much lower intrinsic resistance and improved selectivity to ethanol than sensors S-400 and S-600. X-Ray diffraction(XRD), transmission electron microscopy(TEM) and selective area electron diffraction(SAED) measurements were used to characterize the SnO₂ nanoparticles calcined at different temperatures. The differences in the gas sensing performance of these sensors were analyzed on the basis of scanning electron microscopy(SEM).     

Bi2Sn2O7 nanoparticles attached to SnO2 nanowires and used as catalysts

We introduce a simple method of synthesizing SnO₂ nanowire-Bi₂Sn₂O₇ nanoparticle composites based on the principle that SnO₂ nanowires can be grown by using Bi as catalysts. A mixture of Bi and Sn powders was thermally evaporated, and the effects of growth temperature on the morphology and structure of the products were investigated. We obtained Bi₂Sn₂O₇-tipped SnO₂ nanowires at 700 °C through a vapor–liquid–solid (VLS) process, whereas particle-free SnO₂ nanowires were produced at higher temperatures. We have investigated the oxygen sensing properties of the as-synthesized product.     

Anodic oxidation of formic acid on PdAuIr /C-Sb_2O_5·SnO_2 electrocatalysts prepared by borohydride reduction

PdAuIr/C-Sb2O5·SnO2electrocatalysts with Pd∶Au∶Ir molar ratios of 90∶5∶5,70∶20∶10 and 50∶45∶5 were prepared by borohydride reduction method.These electrocatalysts were characterized by EDX,X-ray diffraction,transmission electron microscopy and the catalytic activity toward formic acid electro-oxidation in acid medium investigated by cyclic voltammetry(CV),chroamperometry(CA)and tests on direct formic acid fuel cell(DFAFC)at 100℃.X-ray diffractograms of PdAuIr/C-Sb2O5·SnO2electrocatalysts showed the presence of Pd fcc phase,Pd-Au fcc alloys,carbon and ATO phases,while Ir phases were not observed.TEM micrographs and histograms indicated that the nanoparticles were not well dispersed on the support and some agglomerates.The cyclic voltammetry and chroamperometry studies showed that PdAuIr/C-Sb2O5·SnO2(50∶45∶5)had superior performance toward formic acid electro-oxidation at 25℃compared to PdAuIr/C-Sb2O5·SnO2(70∶20∶10),PdAuIr/C-Sb2O5·SnO2(90∶5∶5)and Pd/C-Sb2O5·SnO2electrocatalysts.The experiments in a single DFAFC also showed that all PdAuIr/C-Sb2O5·SnO2electrocatalysts exhibited higher performance for formic acid oxidation in comparison with Pd/C-Sb2O5·SnO2electrocatalysts,however PdAuIr/C-Sb2O5·SnO2(90∶5∶5)had superior performance.These results indicated that the addition of Au and Ir to Pd favor the electro-oxidation of formic acid,which could be attributed to the bifunctional mechanism(the presence of ATO,Au and Ir oxides species)associated to the electronic effect(Pd-Au fcc alloys).     

Enhanced Electrochemical Performance of Na0.67Fe0.5Mn0.5O2Cathode with SnO2 Modification

P2-type layered oxide Na_0.67Fe_0.5Mn_0.5O₂ is recognized as a very promising cathode material for sodium-ion batteries due to the merits of high capacity, high voltage, low cost, and easy preparation. However, its unsatisfactory cycle and rate performances remain huge obstacles for practical applications. Here, we report a strategy of SnO₂ modification on P2-type Na_0.67Fe_0.5Mn_0.5O₂ to improve the cycle and rate performance. Scanning electron microscope(SEM) and transmission electron microscope(TEM) images indicate that an insular thin layer SnO₂ is coated on the surface of Na_0.67Fe_0.5Mn_0.5O₂ after medication. The coating layer of SnO₂ can protect Na_0.67Fe_0.5Mn_0.5O₂ from corrosion by electrolyte and the cycle performance is well enhanced. After 100 cycles at 1 C rate(1 C=200 mA/g), the capacity of SnO₂ modified Na_0.67Fe_0.5Mn_0.5O₂ retains 83 mA·h/g(64% to the initial capacity), while the capacity for the pristine Na_0.67Fe_0.5Mn_0.5O₂ is only 38 mA·h/g(33.5% to the initial capacity). X-Ray photoelectron spectroscopy reveals that the ratio of Mn⁴⁺ increases after SnO₂ modification, leading to less oxygen vacancy and expanded lattice. As a result, the capacity of Na_0.67Fe_0.5Mn_0.5O₂ increases from 178 mA·h/g to 197 mA·h/g after SnO₂ modification. Furthermore, the rate performance of Na_0.67Fe_0.5Mn_0.5O₂ is enhanced with SnO₂ coating, due to high electronic conductivity of SnO₂ and expanded lattice after SnO₂ coating. The capacity of SnO₂ modified Na_0.67Fe_0.5Mn_0.5O₂ at 5 C increases from 21 mA·h/g(pristine Na_0.67Fe_0.5Mn_0.5O₂) to 35 mA·h/g.     

PdO,Au, CdO修饰SnO2纳米纤维的制备及其气敏特性

采用静电纺丝的方法制备了SnO₂纳米纤维,并分别用PdO、Au、CdO对该纳米纤维材料进行表面修饰.用X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线能谱(EDX)、X射线光电子能谱(XPS)分析、Brunauer-Emmett-Teller (BET)比表面积测试对材料进行表征.修饰前后, SnO₂纳米纤维都是由约15 nm的纳米颗粒构成的直径约为200 nm的多级结构材料.采用静态测试系统对纯SnO₂及不同物质修饰的SnO₂的气敏特性进行测试,结果表明,未修饰的SnO₂纳米纤维气敏元件对甲醛具有较好的响应.修饰后的SnO₂材料的气敏特性都有明显的改善. CdO修饰的SnO₂气敏元件对甲醛的响应值最高,且响应恢复时间短,选择性好. Au修饰的SnO₂气敏元件对甲醛响应的最佳工作温度从300 ℃降到了200 ℃.经PdO修饰后, SnO₂纳米纤维对甲苯的响应值变得最高.初步分析了经过修饰的SnO₂气敏材料的敏感机理.     

Studies on QCM-type NO2 Gas Sensor Based on Graphene Composites at Room Temperature

Synthetic graphene composite was modified on a transducer of quartz crystal microbalance(QCM) to fabricate a gas sensor for low concentration nitrogen dioxide(NO₂) detection. The gas sensing properties of the QCM coated with SnO₂-rGO and AgNPs-SnO₂-rGO composites were investigated when exposing QCM to low NO₂ con-centration(2.05-20.5 mg/m³) atmosphere at room temperature. The sensing performances of the QCM with AgNPs-SnO₂-rGO composites were enhanced by the introduction of Ag nanoparticles, and the QCM modified with AgNPs-SnO₂-rGO composites could detect NO₂ at room temperature.     

Design of Cr2O3@ZnO Hetero-junction Hierarchical Nanostructures with Enhanced Xylene-sensing Properties

Cr₂O₃@ZnO hetero-junction hierarchical nanostructures were designed to be enhanced xylene sensing material, and thereinto, flower-like ZnO hierarchical nanostructures were synthesized via a solution-based method, and then Cr₂O₃ particles were developed on the surface of ZnO petals via a solvothermal method. From the results of XRD patterns, SEM and TEM images, it can be observed that ZnO has a high-quallity crystallinity and Cr₂O₃ particles scatter uniformly on the suruface of ZnO. The products with different ratios of Cr₂O₃ were used to fabricate gas sensors, and the result indicates that the hetero-junction structures prompt the response to xylene, and the reason may be attributed to the decrease of main carriers concentration caused by the p-n junction between ZnO(n-type semiconductor) and Cr₂O₃(p-type semiconductor), as well as the catalytic oxidation effect on methyl groups of the xylene by Cr₂O₃.     

Pr-PVP掺杂Ti/PbO2电极制备及其在有机物降解中的应用

在Ti基体上,采用电沉积法制备了镨和聚乙烯吡咯烷酮(PVP)掺杂的Ti/SnO₂-Sb₂O₃/Pr₂O₃-PVP-PbO₂ 电极. SEM显示Ti/SnO₂-Sb₂O₃/Pr₂O₃-PVP-PbO₂ 电极表面颗粒细化,镀层结构更加致密和均匀,XRD 测试表明掺杂使可以使电极的表面颗粒变小.循环伏安 (CV)分析表明共掺杂改性后的电极电催化活性明显提高.强化寿命测试显示Ti/SnO₂-Sb₂O₃/Pr₂O₃-PVP-PbO₂ 电极稳定性更好,使用寿命更长. 将所制备的电极应用于亚甲基蓝(MB)模拟染料废水的降解测试,与常规的Ti/PbO₂ 电极相比,Ti/SnO₂-Sb₂O₃/Pr₂O₃-PVP-PbO₂ 电极对亚甲基蓝具有更好的脱色率和 COD 除去率. 降解120min 后,对30 mg·L ^-1 亚甲基蓝的去除率分别可达到99%,对COD去除率为87.9%.     

平面型乙醇快速响应气敏传感器的制备

采用水热法合成了纳米In₂O₃颗粒,将其旋涂于陶瓷基片上经氮化处理获得InN基片,再对InN基片进行氧化,合成出气敏材料并在一种微型平面电极片上制备了传感器件.采用扫描电子显微镜（SEM）、透射电子显微镜（TEM）、X射线衍射（XRD）仪、X射线光电子能谱（XPS）等手段对材料的形貌、组成进行了表征与分析,结果表明,最终获得了松枝状结构的InN-In₂O₃纳米复合材料.对器件的气敏性能进行了测试,发现基于此材料制备的平面型气敏传感器对乙醇气体具有良好的气敏性能：检测浓度为1.025 mg/m³（500 ppb）的乙醇蒸汽的灵敏度可达18;检测2.05 mg/m³（1 ppm）的乙醇的响应-恢复时间最快仅为1 s;最佳工作温度低,仅为50℃.     

分级多孔γ-Al2O3空心微球微波水热法制备及其对刚果红的快速吸附

以KAl(SO₄)₂和尿素为前驱体,通过微波水热法于180 ℃反应20 min,经600 ℃焙烧2 h制得分级多孔γ-Al₂O₃空心微球.所制备的样品被用于吸附典型有机染料刚果红(CR)溶液.结果表明,制备的γ-Al₂O₃空心微球直径为0.8-1.0 μm,厚度约为200 nm.此γ-Al₂O₃空心微球具有高的比表面积(243 m²·g^-1)和分级大孔-中孔结构,此结构非常有利于液相过程中的质量传递.微波水热法制备的γ-Al₂O₃空心微球比水热法制备的γ-Al₂O₃和商用的γ-Al₂O₃样品显示出更快和更强的吸附性能.此样品的吸附数据很好地符合假二级速率方程和Langmuir吸附理论模型.从Langmuir吸附理论模型计算得到微波水热法制备的γ-Al₂O₃空心微球的最大吸附量(q_max) 25 ℃时高达515.4 mg·g^-1.由于具有分等级结构、高比表面积、大的孔容和吸附能力,微波水热法制备的γ-Al₂O₃空心微球样品有望成为一种具有很好应用潜力的环境吸附剂.     

钛基金属氧化物电极制备及其氨氮废水降解性能

采用热分解方法制备了4种电极钛基金属氧化物：Ti/SnO₂+Sb₂O₃、Ti/SnO₂+Sb₂O₃/SnO₂+IrO₂、Ti/SnO₂+Sb₂O₃/SnO₂+RuO₂和Ti/SnO₂+Sb₂O₃/SnO₂+CeO₂. X-射线衍射分析表明Ti/SnO₂+Sb₂O₃/SnO₂+CeO₂电极的CeO₂晶体结构完好,连续工作较长时间电极表面没有明显析氧. 使用该电极电解氧化氨氮模拟废水（降解2 h）,氨氮模拟废水从高浓度（500 mg·L^-1）降解为较低浓度（180 mg·L^-1）,降解效率可达64%,电解活性最佳.     

掺杂Eu2O3的SrTiO3及SnO2光致发光

用具有大能隙的本征半导体(SrTiO₃及SnO₂)粉末作本体,分别掺杂1%(原子百分数)的Eu₂O₃;所得物质表现出Eu³⁺离子的线发射光谱特性,但相对发光强度及光谱形状有相当大的变化。X射线衍射结构分析显示Eu³⁺在SrTiO₃晶格里是处在间隙位置,而它在SnO₂晶格里则形成新物相Eu₂Sn₂O₇。     

Electrochemical performance of a nano SnO2-modified LiNi1/3Co1/3Mn1/3O2 cathode material

The nano SnO₂-modified LiNi_1/3Co_1/3Mn_1/3O₂ was successfully prepared by a carrier transfer method. The pristine and modified samples were characterized with various techniques such as XRD, SEM, XPS and EDS. The results showed that the SnO₂ particles did not enter the crystal structure of LiNi1/3Co1/ 3Mn1/3O₂, many nano SnO₂ particles were uniformly covered on the surface of LiNi_1/3Co_1/3Mn_1/3O₂ and the modified thin layer could inhibit the dissolution of transition metal oxides. The electrochemical tests indicated that the existence of nano SnO₂ could improve the discharge capacity and rate capability owing to the decreased interfacial polarization. The cycling stability was remarkably improved at room temperature and 55 ℃. The XRD patterns of the fresh NCM electrode and after 50 cycles proved that the structural change of NCM was not so effective on the capacity fade.     

Rational Fabrication of Size Tunable SnO2 Hollow Microspheres

A designed solution route was developed to fabricate size tunable SnO₂ hollow microspheres based on the sol-gel theory. The hydrolysis of SnSO₄ released protons to form SnO₂ particulates and induced the decrease of pH value. To minimize the high surface energy, the SnO₂ particulates tended to assemble into large particles, the size of which was affected by the electrolyte concentration or pH value. Elevating SnSO₄ content aroused the decrease of the pH value that directed to the shrinkage of the aggregated particle size of SnO₂. Size tunable SnO₂ hollow microspheres were then rationally fabricated under solvothermal conditions via Ostwald ripening by simply adjusting the SnSO₄ concentration. The in situ pH decrease directed to the shrinkage of the particle size from 270 nm to 112 nm. The formation mechanism was confirmed and rationally elucidated by the time dependant morphology evolution. Charge-discharge tests revealed that the reduced particle size aroused an improved lithium ion battery performance.     

Ultraviolet Light Assisted Hierarchical Porous Fe2O3 Catalyzing Heterogeneous Fenton Degradation of Tetracycline Under Neutral Condition with a Low Requirement of H2O2

The hierarchical porous Fe2O3 particles as a novel ultraviolet light assisted heterogeneous Fenton catalysts were synthesized by bio-template synthesis method using iron nitrate as precursor at high temperature of around 550℃.The hierarchical porous structured Fe2O3 was endowed with a large surface area and abundant pore volume,leading to the exposure of more active sites and rapid mass transfer.The synergistic effect of UV irradiation and hie-rarchical porous Fe2O3 improved the photo-degradation efficiency of Tetracycline(TC).The degradation efficiency of Fe203 catalyzing UV-Fenton system reached 97.4%after 60 min reaction,which was more substantial than Fe2O3 catalyzing Fenton system(7.6%)and UV/H2O2 system(59.2%).Moreover,the hierarchical porous Fe2O3 catalyzing UV-Fenton system exhibited an extremely wide pH range(from 3.0 to 9.0,from mildly acidic to slightly alkaline)for efficient degradation of TC.Simultaneously,the extraordinary higher degradation efficiency was based on 10 mmol/L H2O2 concentration,which was low requirement for H2O2,Further,the hierarchical porous Fe2O3 can be used for five consecutive cycles with over 95%of the original degradation efficiency.Ultraviolet light assisted heterogeneous Fenton reaction in the hierarchical porous Fe2O3 improved the·OH and O2·^-production and Fe(III)/Fe(II)redox cycle,which consequently achieved an excellent degradation rate.     

气敏半导体材料Cd2Sb2O6.8的制备及其性能研究

采用化学共沉淀法,在较低温度(750℃)下制备了具有缺陷烧绿石结构的复合氧化物Cd₂Sb₂O_6.8的纯相超微粉;研究了制备条件对物相、结构和气敏性能的影响,并对其反应过程机理进行了探讨,气敏性能测试结果表明,纯相Cd₂Sb₂O_6.8气敏元件对乙炔气体有较高的灵敏度和较好的选择性.     

纳米晶Sb掺杂SnO2(ATO)粉体的合成与表征

以Sn粉和Sb₂O₃为原料.采用共沉淀法制备了纳米ATO粉.TG-DSC及FTIR结果表明.450℃以前前驱体已失去全部水分.并完全转化为氧化物.XRD测量结果表明.所得ATO粉具有四方金红石结构.500℃焙烧后粉体的粒径为12nm.随着焙烧温度的升高.粉体的粒径增加.TEM测定结果表明,粉体的分散性很好.团聚很少.粉体的烧结性能良好,950℃时烧结5h即达到理论密度的97.3％.用霍尔系数法测定粉体的导电行为.表明该粉体具有良好的导电性能.     

Pt/DNA-MWCNTs/GC电极制备及其H2O2还原的电催化活性

将DNA功能化多壁碳纳米管（MWCNTs）复合材料修饰于玻碳基底（GC）表面制得DNA-MWCNTs/GC电极,并在此基础上电沉积负载Pt纳米颗粒构建了一种新型无酶H₂O₂传感电极. 利用扫描电子显微镜（SEM）表征制得的修饰电极,同时通过循环伏安法和计时电流法研究了该传感电极的H2O2响应性能. 结果表明,该传感电极的H₂O₂检测在0.04 ~ 18.07 mmol·L^-1浓度范围内成线性相关,检出限3.85 μmol·L^-1（S/N = 3）,且有良好的重现性、稳定性与选择性.