In、Sn和Ti纳米复合物对CH4气敏和催化性能研究

用可控湿化学共沉淀法研制了In₂O₃-SnO₂纳米复合物，通过控制金属盐浓度、阳离子比、沉淀pH值和老化时间，制得化学均一的两元复合物，引入适量的第三组分TiO₂制得三元纳米复合氧化物，研究了TiO₂添加对材料气敏和CH₄催化反应活性的影响，用各种分析方法对复合物进行物性和结构表征，从对CH₄气敏和催化活性测定的结果表明，两元25%In₂O₃-75%SnO₂复合物和三元(25%In₂O₃-75%SnO₂)-20%TiO₂复合物对CH₄具有较好的灵敏度和催化活性，两者有相同变化趋势，也提高了对CO的选择性，再经过掺杂对基质进行结构调变和表面修饰，进一步提高气敏和催化活性。用程序升温吸-脱附(TPD)实验和X-射线光电子能谱(XPS)分析研究了纳米复合物表面对待测气体和氧的吸脱附行为和组分间电子和化学的相互作用，探讨了气敏机制。     

CuO/Cu2(OH)2CO3梭型中空颗粒的制备及其气敏性能

以Cu₂(OH)₃NO₃为前驱体,采用无模板溶剂热法成功合成了大小为1~2 μm的CuO/Cu₂(OH)₂CO₃中空梭型微粒.高倍电镜显示其外壳层由高度弥散的CuO和Cu₂(OH)₂CO₃纳米颗粒组成.通过控制反应时间证明了该中空梭型粒子的形成过程是由自组装和奥斯特瓦尔德熟化过程控制.该纳米材料的特殊结构使其对乙醇、丙酮等有机气体有良好的气敏性能.     

NO气体在TiO2表面的吸附行为

采用TPD (Temperature Programmed Desorption)试验方法测定了NO在TiO₂表面吸附后的脱附谱, 揭示了气体脱附量的变化规律. 结果表明, NO在TiO₂表面吸附后可在两个峰值温度450和980 K脱附出N₂气体, 其活化能分别是0.48 和2.5 eV. TiO₂表面经预覆氧处理后, N₂的脱附量降低. N₂的脱附量随NO气体暴露量增加而增加, 但当气体覆盖度超过一定值后, 脱附量趋于定值. 脱附峰值温度随气体暴露量的增加而降低.     

CuO/Cu2(OH)2CO3梭型中空颗粒的制备及其气敏性能

以Cu₂(OH)₃NO₃为前驱体,采用无模板溶剂热法成功合成了大小为1~2μm的CuO/Cu₂(OH)₂CO₃中空梭型微粒。高倍电镜显示其外壳层由高度弥散的CuO和Cu₂(OH)₂CO₃纳米颗粒组成。通过控制反应时间证明了该中空梭型粒子的形成过程是由自组装和奥斯特瓦尔德熟化过程控制。该纳米材料的特殊结构使其对乙醇、丙酮等有机气体有良好的气敏性能。     

NO气体在TiO2表面的吸附行为

采用TPD (Temperature Programmed Desorption)试验方法测定了NO在TiO₂表面吸附后的脱附谱, 揭示了气体脱附量的变化规律. 结果表明, NO在TiO₂表面吸附后可在两个峰值温度450和980 K脱附出N₂气体, 其活化能分别是0.48 和2.5 eV. TiO₂表面经预覆氧处理后, N₂的脱附量降低. N₂的脱附量随NO气体暴露量增加而增加, 但当气体覆盖度超过一定值后, 脱附量趋于定值. 脱附峰值温度随气体暴露量的增加而降低.     

纳米TiO2低温水解法的晶型控制合成及其表面织构的研究

分别以TiCl₄，Ti(NO₃)₄和Ti(SO₄)₂为前驱体，在低温和强酸性条件下，通过水解反应可控地合成了具有不同晶相组成，且比表面积较高的纳米TiO₂，并用XRD，TEM和N₂^-吸附脱附技术对其晶相、粒径大小、形貌及比表面积进行了表征。结果表明，钛离子在有Cl^-、NO₃^-存在的酸性溶液中水解，水解温度≤80 ℃，可以生成结晶良好的具有细小晶粒尺寸和较高比表面积的金红石型纳米TiO₂粉体，水解温度>80 ℃，反而有锐钛矿型TiO₂生成，而在有SO₄^2-存在的酸性溶液中，TiO₂样品的晶相组成不随水解温度的变化而改变，均为锐钛矿型，其比表面积可达300 m²·g^-1。     

Ni/SiO2-Al2O3催化乙酰丙酸加氢制γ-戊内酯

采用溶胶-凝胶法制备了一系列不同Al₂O₃含量的SiO₂-Al₂O₃复合氧化物,以该系列复合氧化物为载体,采用等体积浸渍法制备了Ni负载量15%（重量百分比）的催化剂,用于催化乙酰丙酸加氢制γ-戊内酯.采用N₂物理吸附、X射线衍射（XRD）、H₂程序升温还原（H₂-TPR）、H₂程序升温脱附（H₂-TPD）、NH₃程序升温脱附（NH₃-TPD）和吡啶吸附红外（Py-IR）等手段对催化剂进行了表征.结果表明,不同载体催化剂的活性组分分散度及表面酸性质存在明显差异,显著影响了催化剂吸附、活化H₂与C=O键的能力,进而影响了催化剂的乙酰丙酸加氢活性.其中,Ni/SiO₂-Al₂O₃催化剂上的L酸中心能够促进C=O键的吸附、活化,与金属Ni上的H₂吸附活性位协同作用,大大提高了乙酰丙酸加氢活性.因此,具有最多L酸中心和丰富H₂吸附活性位的Ni/SiO₂-8Al₂O₃催化剂表现出最高的乙酰丙酸加氢活性,在180℃、4 MPa氢气压力下,乙酰丙酸转化率达到90.5%,目标产物γ-戊内酯选择性为100%.     

不同形貌纳米CoWO4的水热法制备及气敏性能

以Co（NO₃）₂·6H₂O、Na₂WO₄·2H₂O为主要原料,去离子水为溶剂,利用水热法在不同条件下制备了一系列的纳米CoWO₄,用XRD、TEM和比表面分析仪对产品的物相、形貌和比表面积进行了表征。较系统地探讨了水热条件（反应混合物pH值、反应时间、反应温度等）对产物物相和形貌的影响,并研究了不同形貌产品对甲醛、乙醇、氨气、苯和丙酮等的敏感性能。结果表明：水热条件对产品的物相和形貌有影响,在不同水热条件下,可成功制备CoWO₄纳米颗粒、纳米立方体及纳米棒;以纳米颗粒、纳米立方体及纳米棒样品制成的气敏元件对被试气体有不同程度的响应,其中以纳米颗粒为基的元件在210℃对1000μL·L^-1NH₃灵敏度为3.3。     

MoS2/Cd2SnO4复合材料的制备及其气敏性能

采用水热-煅烧法制备Cd₂SnO₄,之后通过超声混合法得到一系列MoS₂/Cd₂SnO₄复合材料。采用X射线衍射、扫描电子显微镜、X射线光电子能谱对Cd₂SnO₄和一系列MoS₂/Cd₂SnO₄复合材料进行结构和形貌的表征。研究了MoS₂掺杂量对于MoS₂/Cd₂SnO₄复合材料的气敏性能影响。实验结果表明,当MoS₂与Cd₂SnO₄的质量比为2.5%,MoS₂/Cd₂SnO₄复合材料制备的气敏元件在170 ℃时对浓度为100 μL·L^-1的甲醛气体的灵敏度为40.0,最低检测限为0.1 μL·L^-1。     

Ni-Cu-Mn-K/γ-Al2O3高温变换催化剂的结构和性能表征

以γ-Al₂O₃为载体，采用二步等体积浸渍法，制备了Ni-Cu-Mn-K/γ-Al₂O₃高温水煤气变换催化剂。采用低温氮吸附-脱附，DTA，XRD，H₂-TPR等方法对催化剂进行了表征，比较了载体、单组分、双组分、以及多组分浸渍的样品结构及各物种的存在形式，探讨了催化剂的活性相组成。结果表明，所制备的催化剂具有较大的比表面积，孔径呈介孔分布结构;低温时，催化剂活性相主要为高度分散的Cu、Ni、Ni-Cu-O、xCuO·yMnO₂和xNiO·yMnO₂复合氧化物;高温时，活性相可能为 xCuO·yMnO₂和xNiO·yMnO₂等复合氧化物。经530 ℃耐热15 h后催化活性测试结果分析认为，活性相xCuO·yMnO₂和xNiO·yMnO₂等复合氧化物提高了该催化剂的热稳定性。     

Reduced graphene oxide-porous In2O3 nanocubes hybrid nanocomposites for room-temperature NH3 sensing

Metal oxide semiconductors(MOS)-reduced graphene oxide(rGO) nanocomposites have attracted great attention for room-tempe rature gas sensing applications.The development of novel sensing materials is the key issue for the effective detection of ammoniagas at room temperature.In the present work,the novel reduced graphene oxide(rGO)-In₂ O₃ nanocubes hybrid materials have been prepared via a simple electrostatic self-assembly strategy.Characterization re sults exhibit that the...     

Synthesis of Ag Nanoparticle Doped MnO2/GO Nanocomposites at a Gas/Liquid Interface and its Application in H2O2 Detection

Ag/MnO₂/GO nanocomposites were synthesized via the method of gas/liquid interface based on silver mirror reaction, and a non‐enzymatic H₂O₂ sensor was fabricated through immobilizing Ag/MnO₂/GO nanocomposites on GCE. The composition and morphology of the nanocomposites were studied by energy‐dispersive X‐ray spectroscopy (EDS), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Electrochemical investigation indicated that it exhibited a favorable performance for the H₂O₂ detection. Its linear detection range was from 3 μM to 7 mM with a correlation coefficient of 0.9960; the sensitivity was 105.40 μA mM^?1 cm^?2 and the detection limit was estimated to be 0.7 μM at a signal‐to‐noise ratio of 3.     

Ethanol Gas Sensor Based on γ-Fe2O3 Nanoparticles Working at Room Temperature with High Sensitivity

Improving the sensing sensitivity and lowering the working temperature are the critical issues for the practical application of gas sensors. For a gas sensor, the sensing materials play important roles in determining the sensing properties. In the present work, γ-Fe₂O₃ microspheres composed of nanoparticles were successfully fabricated by a typical facile hydrothermal process and a following annealing treatment. Interestingly, the as-synthesized γ-Fe₂O₃ microspheres showed excellent sensing properties for the detection of ethanol gas with high sensitivity, and especially working temperature as low as room temperature. The gas sensing results showed that at the optimal operating temperature (200 °C), the response intensity of γ-Fe₂O₃ microspheres for 1000 ppm ethanol gas could reach 74.6 and the limit of detection (LOD) was about 0.026 ppm. At room temperature, the γ-Fe₂O₃ microspheres still demonstrated a good response to different concentrations of ethanol gas from 1 to 1000 ppm, with a very good selectivity over other gas species and a good stability. This study indicated that the γ-Fe₂O₃ phase could be a type of promising room-temperature gas sensing material for ethanol gas detection.     

On‐Chip Tailorability of Capacitive Gas Sensors Integrated with Metal–Organic Framework Films

Gas sensing technologies for smart cities require miniaturization, cost‐effectiveness, low power consumption, and outstanding sensitivity and selectivity. On‐chip, tailorable capacitive sensors integrated with metal–organic framework (MOF) films are presented, in which abundant coordinatively unsaturated metal sites are available for gas detection. The in situ growth of homogeneous Mg‐MOF‐74 films is realized with an appropriate metal‐to‐ligand ratio. The resultant sensors exhibit selective detection for benzene vapor and carbon dioxide (CO₂) at room temperature. Postsynthetic modification of Mg‐MOF‐74 films with ethylenediamine decreases sensitivity toward benzene but increases selectivity to CO₂. The reduced porosity and blocked open metal sites caused by amine coordination account for a deterioration in the sensing performance for benzene (by ca. 60 %). The enhanced sensitivity for CO₂ (by ca. 25 %) stems from a tailored amine–CO₂ interaction. This study demonstrates the feasibility of tuning gas sensing properties by adjusting MOF–analyte interactions, thereby offering new perspectives for the development of MOF‐based sensors.     

Facile synthesis of mesoporous WO3@graphene aerogel nanocomposites for low-temperature acetone sensing

Nanocomposites constructed by combining mesoporous metal oxides and graphene have received tremendous attention in wide fields of catalysis,energy storage and conversion,gas sensing and so on.Herein,we present a facile interface-induced co-assembly process to synthesize the mesoporous W03@graphene aerogel nanocomposites(denoted as mW03@GA),in which graphene aerogel(GA) was used as a macroporous substrate,mesoporous W03 was uniformly coated on both sides of graphene sheets through a solvent evaporation-induced self-assembly(EISA) strategy using diblock copolymer poly(ethylene oxide)-b-polystyrene(PEO-b-PS) as a template.The resultant mW03@GA nanocomposites possess well-interconnected macroporous graphene networks covered by mesoporous W03 layer with a uniform pore size of 19 nm,high surface area of 167 m~2/g and large pore volume of 0.26 cm~3/g.The gas sensing performance of mW03@GA nanocomposites toward acetone and other gases was studied,showing a high selectivity and great response to acetone at low temperature of 150℃,which could be developed as a promising candidate as novel sensors for VOCs detection.     

A WO3 nanorod-Cr2O3 nanoparticle composite for selective gas sensing of 2-butanone

The sensor based on WO₃-Cr₂O₃ nanocomposites show good selectivity to 2-butanone.     

High ethanol sensitivity of Palladium/TiO2 nanobelt surface heterostructures dominated by enlarged surface area and nano-Schottky junctions

TiO₂ nanobelts were prepared by the hydrothermal growth method. The surface of the nanobelts was coarsened by selective acid corrosion and functionalized with Pd catalyst particles. Three nanobelt samples (TiO₂ nanobelts, surface-coarsened TiO₂ nanobelts and Pd nanoparticle/TiO₂ nanobelt surface heterostructures) were configured as gas sensors and their sensing ability was measured. Both the surface-coarsened nanobelts and the Pd nanoparticle-decorated TiO₂ nanobelts exhibited dramatically improved sensitivity to ethanol vapor. Pd nanoparticle-decorated TiO₂ nanobelts with surface heterostructures exhibited the best sensitivity, selectivity, working temperature, response/recovery time, and reproducibility. The excellent ethanol sensing performance is attributed to the large surface area and enhancement by Schottky barrier-type junctions between the Pd nanoparticles and TiO₂ nanobelts.     

Hybrid ZnO/SWNT Nanostructures Based Gas Sensor

Zinc oxide (ZnO) nanoparticles decorated single walled carbon nanotubes (SWNTs) were electrochemically synthesized where the deposition conditions were systematically explored to tailor the size, density, and microstructure of the ZnO nanoparticles and correlated to the gas sensing performance. Room temperature conductometric detection of various analytes including CO, CO₂, NO₂, NH₃, SO₂, H₂S with ZnO/SWNT hybrid nanostructures demonstrated uncharacteristic selectivity towards H₂S with little to no response for the other analytes examined. Optimal ZnO/SWNTs gas sensor devices showed a significantly increased in H₂S sensitivity over unfunctionalized SWNT networks (i.e. 4.96 % per ppm_V vs. 0.225 % ppm_V) with a lower detection limit in the ppb range. Additionally, the H₂S sensing performance was greatly improved by enhancing the crystallinity of ZnO nanoparticles.     

Hierarchical NiCo2O4 microspheres assembled by nanorods with p-type response for detection of triethylamine

The morphological and structural design provides an efficient protocol to optimize the performance of gas sensing materials. In this work, a gas sensor with high sensitivity for triethylamine (TEA) detection is developed based on p-type NiCo₂O₄ hierarchical microspheres. The NiCo₂O₄ microspheres, synthesized by a hydrothermal route, have a three-dimensional (3D) urchin-like structure assembled by nanorod building blocks. The structure-property correlation has been investigated by powder X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscope, scanning electron microscope, N₂ adsorption-desorption tests and comprehensive gas sensing experiments. The influence of calcination temperature on the morphological structure and sensing performances has been investigated. Results reveal that the material annealed at 300 °C has a very large specific surface area of 125.27 m²/g, thereby demonstrating the best TEA sensing properties including high response and low limit of detection (145 ppb), good selectivity and stability. The further increase of the calcination temperature leads to the collapse of the 3D hierarchical structure with significantly decreased surface area, which is found to decline the sensing performances. This work indicates the promise of ternary p-type metal oxide nanostructures for application in highly sensitive gas sensors.     

Resistive-type sensors based on few-layer MXene and SnO2 hollow spheres heterojunctions: Facile synthesis,ethanol sensing performances

High-performance and low-cost gas sensors are highly desirable and involved in industrial production and environmental detection. The combination of highly conductive MXene and metal oxide materials is a promising strategy to further improve the sensing performances. In this study, the hollow SnO₂ nanospheres and few-layer MXene are assembled rationally via facile electrostatic synthesis processes, then the SnO₂/Ti₃C₂T_x nanocomposites were obtained. Compared with that based on either pure SnO₂ nanoparticles or hollow nanospheres of SnO₂, the SnO₂/Ti₃C₂T_x composite-based sensor exhibits much better sensing performances such as higher response (36.979), faster response time (5 s), and much improved selectivity as well as stability (15 days) to 100 ppm C₂H₅OH at low working temperature (200 °C). The improved sensing performances are mainly attributed to the large specific surface area and significantly increased oxygen vacancy concentration, which provides a large number of active sites for gas adsorption and surface catalytic reaction. In addition, the heterostructure interfaces between SnO₂ hollow spheres and MXene layers are beneficial to gas sensing behaviors due to the synergistic effect.