三氯乙烯气相光催化氧化研究

本文以纳米颗粒TiO2为活性组分，制备了不同的负载化催化剂，并对三氯乙烯（TCE)气相光催化氧化过程进行了研究。实验结果表明在近紫外光的照射下，气相污染物可被迅速降解。载体不仅起到固定添组分的作用，而且其吸附作用有助于更好地发挥活性组分的摧化活性。     

金原子簇催化应用的研究进展

在最近的10年里,原子精确的金原子簇(AunLm,L为有机配体)已经被证明是一种新型的纳米金催化剂.不同尺寸的AunLm催化剂表现出独特的电子和晶体结构,为关联催化性能和催化剂结构的内在关系及研究纳米金催化的化学反应机制提供了新的研究平台.在这篇综述中,主要介绍金原子簇催化剂在催化反应中的应用,如选择性氧化和加氢,及C—C偶联反应等,同时,也讨论金原子簇催化剂的尺寸效应、配体效应(例如,芳香族vs脂肪族)、杂金属掺杂(如铜、银、钯、铂)等.最后,在原子尺度上研究了金原子簇催化的反应机制以及结构-活性的构建关系.     

碳载体对PtRu/C催化剂性能的影响研究

本文采用水热方法合成不同粒径和形貌的碳球,并将其作为载体,采用化学镀的方法制备PtRu/C催化剂;应用XRD、SEM和TEM对碳球及催化剂的结构和形貌进行表征。采用电化学方法测试不同形貌碳球的比表面积以及碳球担载催化剂的催化活性,结果表明,水热反应条件对碳球的粒径及形貌影响显著,三种碳球担载催化剂的活性按照以下顺序衰减：多孔的粒径约为100nm的碳球担载PtRu催化剂优于连体碳球优于直径约500nm的单分散碳球担载催化剂。TEM分析结果表明,在碳球表面化学镀的PtRu纳米颗粒均匀分散在碳载体表面,其平均粒径约为3nm。电化学测试表明粒径为100nm的多孔碳球的电化学比表面积较大,以这种碳球为载体的PtRu/C催化剂对甲醇氧化的催化性能较高。     

Synthesis of Au–Ag alloy nanoparticles supported on silica gel via galvanic replacement reaction

Synthesis of supported Au-Ag bimetallic has attracted much attention since we found for the first time that Au and Ag had synergistic effect on CO oxidation and preferential CO oxidation in rich hydrogen.In this work,the formation of Au-Ag alloy nanoparticles supported on silica gel by galvanic replacement reaction has been investigated.We applied various characterizations including X-ray diffraction(XRD),transmission electronic microscopy(TEM),ultraviolet-visible spectroscopy(UV-vis),X-ray absorption spectroscopy(XAS) to characterize the formation process of Au-Ag alloy.Although the average particle sizes of the Au-Ag alloy nanoparticles obtained by the galvanic replacement reaction are relatively large comparing with that of loading Au first,the catalytic activity of the catalyst in preferential CO oxidation is almost the same.This result manifested that the particle size effect of Au-Ag nanoparticles was not as tremendous as that of monometallic gold.The formation of Au-Ag alloy made it less sensitive to the particle size.     

在超临界流体中将PtRu纳米粒子沉积在石墨烯片层及其电催化性能研究

在超临界二氧化碳的辅助下,使用乙酰丙酮铂和乙酰丙酮钌作为前驱体,甲醇作为共溶剂,H2作为还原剂,在200℃将PtRu纳米颗粒还原负载在石墨烯（EG）上.制备产物的形貌和微结构用X射线衍射（XRD）、X射线光电子能谱（XPS）和透射电子显微镜（TEM）进行了分析.同时,用相同的方法制备了PtRu/C（炭黑Vulcan XC-72）复合材料,将其与PtRu/EG对于甲醇氧化的电催化活性和稳定性也通过循环伏安和计时电流法进行了比较.研究证实,用超临界流体方法沉积在石墨烯上的PtRu纳米颗粒具有较小的平均粒径和尺寸分布.与PtRu/C相比,PtRu/EG复合材料对于甲醇电氧化展示出更高的电催化活性和稳定性.     

Tunable gold catalysts for selective hydrocarbon oxidation under mild conditions

Oxidation is an important method for the synthesis of chemical intermediates in the manufacture of high-tonnage commodities, high-value fine chemicals, agrochemicals and pharmaceuticals: but oxidations are often inefficient. The introduction of catalytic systems using oxygen from air is preferred for 'green' processing. Gold catalysis is now showing potential in selective redox processes, particularly for alcohol oxidation and the direct synthesis of hydrogen peroxide. However, a major challenge that persists is the synthesis of an epoxide by the direct electrophilic addition of oxygen to an alkene. Although ethene is epoxidized efficiently using molecular oxygen with silver catalysts in a large-scale industrial process, this is unique because higher alkenes can only be effectively epoxidized using hydrogen peroxide, hydroperoxides or stoichiometric oxygen donors. Here we show that nanocrystalline gold catalysts can provide tunable active catalysts for the oxidation of alkenes using air, with exceptionally high selectivity to partial oxidation products ( approximately 98%) and significant conversions. Our finding significantly extends the discovery by Haruta that nanocrystalline gold can epoxidize alkenes when hydrogen is used to activate the molecular oxygen; in our case, no sacrificial reductant is needed. We anticipate that our finding will initiate attempts to understand more fully the mechanism of oxygen activation at gold surfaces, which might lead to commercial exploitation of the high redox activity of gold nanocrystals.     

Hydrogen generation from decomposition of hydrous hydrazine over Ni-Ir/CeO2 catalyst

The synthesis of highly active and selective catalysts is the central issue in the development of hydrous hydrazine(N_2H_4·H_2O) as a viable hydrogen carrier. Herein, we report the synthesis of bimetallic Ni-Ir nanocatalyts supported on CeO_2 using a one-pot coprecipitation method. A combination of XRD, HRTEM and XPS analyses indicate that the Ni-Ir/CeO_2 catalyst is composed of tiny Ni-Ir alloy nanoparticles with an average size of around 4 nm and crystalline CeO_2 matrix. The Ni-Ir/CeO_2 catalyst exhibits high catalytic activity and excellent selectivity towards hydrogen generation from N_2H_4·H_2O at mild temperatures. Furthermore, in contrast to previously reported Ni-Pt catalysts, the Ni-Ir/CeO_2 catalyst shows an alleviated requirement on alkali promoter to achieve its optimal catalytic performance.     

Catalytic combustion properties of nanocomplex oxide for natural gas

The catalysts of copper oxide supported on cerium dioxide were prepared by different methods for methane catalytic combustion. The effects of copper content in the catalysts and calcination temperatures of the catalysts on the catalytic activity are investigated. Results show that the complex oxide catalyst exhibits high catalytic activity for methane combustion due to the synergistic effect of CuO and CeO₂. The catalyst prepared by impregnation is more active than that prepared by controlled coprecipitation even if CuO content is the same. When W(CuO)<13%, the light-off temperature and full conversion temperature for the CH₄ reaction decrease with the increasing of CuO content in the catalysts. However, when the copper content is above 13%, the excess CuO has a negative effect on the catalytic activity owing to the formation of bulk CuO particles. A proper calcinations temperature of 650 ℃ can lead to a high dispersion of CuO and accordingly can enhance the catalytic activity of the composites.     

Three-dimensional atomic-scale structure of size-selected gold nanoclusters

An unambiguous determination of the three-dimensional structure of nanoparticles is challenging. Electron tomography requires a series of images taken for many different specimen orientations. This approach is ideal for stable and stationary structures. But ultrasmall nanoparticles are intrinsically structurally unstable and may interact with the incident electron beam, constraining the electron beam density that can be used and the duration of the observation. Here we use aberration-corrected scanning transmission electron microscopy, coupled with simple imaging simulation, to determine with atomic resolution the size, three-dimensional shape, orientation and atomic arrangement of size-selected gold nanoclusters that are preformed in the gas phase and soft-landed on an amorphous carbon substrate. The structures of gold nanoclusters containing 3096 atoms can be identified with either Ino-decahedral, cuboctahedral or icosahedral geometries. Comparison with theoretical modelling of the system suggests that the structures are consistent with energetic considerations. The discovery that nanoscale gold particles function as active and selective catalysts for a variety of important chemical reactions has provoked much research interest in recent years. We believe that the detailed structure information we provide will help to unravel the role of these nanoclusters in size- and structure-specific catalytic reactions. We note that the technique will be of use in investigations of other supported ultrasmall metal cluster systems.     

Mesoporous iron oxide-silica supported gold catalysts for low-temperature CO oxidation

Mesoporous iron oxide-silica composite with a high silica content was synthesized by hydrothermal method, and another composite material with a high iron content was obtained by etching part of silica in alkaline solution. Gold catalysts were loaded onto both composites by a deposition-precipitation method, and used for CO oxidation. The samples were characterized by Brumauer- Emmet-Teller （BET）, X-ray diffraction （XRD）, X-ray photoelectron spectra （XPS）, transmission electron micro- scope （TEM） and scanning electron microscope （SEM） techniques. Both composites had high specific surface areas and were amorphous. The Au nanoparticles dispersed on the surface of the composites existed in metallic state. Composite with high silica content was not suitable for Au loading, and its supported gold catalyst showed poor per- formance in catalytic reaction. In contrast, composite with high iron content allowed efficient Au loading, and CO could be oxidized completely at low temperature on its supported gold catalyst. The effects of deposition-precipi- tation pH values on Au loading and activity of the catalyst were investigated, and the results indicated that Au loading was the highest and the catalyst was the most active for CO oxidation when the synthesis pH was adjusted to 8.     

负载型Au/Al2O3系列催化剂的研究进展

负载型金催化剂作为一种新型催化剂,它优异的催化氧化性能引起越来越多化学工作者的关注.Au/Al₂O₃是催化剂制备中大量使用的典型氧化物载体.综述了近年来以Au/Al₂O₃为载体的系列Au/Al₂O₃催化剂的制备方法、催化性能及其活性中心结构的研究状况和发展趋势,讨论的主要反应包括CO低温催化氧化为CO₂、汽车尾气净化、含卤有机化合物的消除和甲烷催化燃烧.     

Synthesis and size control of gold nanoparticles in regular system of amphiphilic molecules

Two synthetic techniques for colloidal gold particles was improved by using SDS. And colloidal Au particles of mean diameters between 5 and 14 nm are synthesized, that exhibit improved monodispersity relative to previously published methods. According to the particular molecular structure of surfactants and different electrons distribution arising from colloidal small sizes and high surface/ volume ratios, it is found that there are a complex between SDS and Au³⁺ (and Au atoms ) during synthesizing colloidal gold nanoparticles and as a stablizer for Au particles, SDS can prevent their further growth. So the colloidal gold particles is monodispersize and more steady. But other surfactants don't affect the process of synthesizing gold nanoparticles because of their structures and properties different from SDS. Gold nanoparticles have considerable bioaffinity and can be applied to study the adsorption of proteins or polypeptides.     

新型高级氧化技术在污水处理中的应用

为了能够对污水中有毒难生物降解的有机污染物进行更加有效的处理，采用了一种V-O型高级催化氧化技术，通过试验初步探讨了其催化机理、催化性能和活性及其影响因素。试验结果表明，在自制的6种催化剂中，V-O／SiO2／N2显示了较好的催化性能和活性；其催化机理为催化剂和臭氧反应。生成了氧化性极强的羟基自由基；催化臭氧化时间、催化剂用量、进气臭氧浓度、体系pH值等因素均对降解产生一定的影响。研究结果为该技术在环境保护领域的应用前景提供了可靠的理论根据。     

Surface modifications of Pt-based atomically ordered nanoparticles to improve catalytic performances for oxygen reduction reaction

Bimetallic platinum-cobalt (Pt–Co) nanostructure catalysts represent superior catalytic performances for oxygen reduction reaction (ORR). In a variety of Pt–Co catalyst structures, atomically ordered structure catalysts show excellent catalytic performances in the ORR. In this work, for promoting their catalytic performances, atomically ordered PtCo nanoparticles (PtCo/C) with carbon supported were successfully prepared by an improved impregnation method and annealing. Then, the ordered PtCo/C catalysts have been significantly improved by doped with ultralow amount of Au and Cr transition metal. The physical and electrochemical test results demonstrate the Cr–PtCo/C and Au–PtCo/C catalysts have superior catalytic performances including mass activity and stability compared to commercialized Johnson Matthey (JM) Pt/C, which was the result of the modified electronic properties of Pt surface and atomically ordered structure. The presence of Au and Cr enhances the stability of PtCo/C catalysts. This work represents a simple way to promote the catalytic performances of the atomically ordered catalysts.     

Observation of ligand effects during alkene hydrogenation catalysed by supported metal clusters

Homogeneous organometallic catalysts and many enzymes activate reactants through coordination to metal atoms; that is, the reactants are turned into ligands and their reactivity controlled through other ligands in the metal's coordination sphere. In the case of supported metal clusters, catalytic performance is influenced by the support and by adsorbed reactants, intermediates or products. The adsorbates are usually treated as ligands, whereas the influence of the supports is usually ascribed to electronic interactions, even though metal clusters supported on oxides and zeolites form chemical bonds to support oxygen atoms. Here we report direct observations of the structure of supported metal clusters consisting of four iridium atoms, and the identification of hydrocarbon ligands bound to them during propene hydrogenation. We find that propene and molecular hydrogen form propylidyne and hydride ligands, respectively, whereas simultaneous exposure of the reactants to the supported iridium cluster yields ligands that are reactive intermediates during the catalytic propane-formation reaction. These intermediates weaken the bonding within the tetrahedral iridium cluster and the interactions between the cluster and the support, while replacement of the MgO support with gamma-Al2O3 boosts the catalytic activity tenfold, by affecting the bonding between the reactant-derived ligands and the cluster and therefore also the abundance of individual ligands. This interplay between the support and the reactant-derived ligands, whereby each influences the interaction of the metal cluster with the other, shows that the catalytic properties of supported metal catalysts can be tuned by careful choice of their supports.     

超声波辅助下海螵蛸负载二氧化锰催化降解染料的研究

采用三种不同的方法制备海螵蛸负载二氧化锰催化剂，研究了催化剂对苋菜红、次甲基蓝和酸性湖蓝A三种染料的催化超声降解性能，并从催化剂中MnO₂负载量及染料的化学结构两方面分析了降解性能的差异，探讨超声降解的机理，同时研究了三种染料超声降解过程的动力学分析。结果表明，用高锰酸钾氧化法制备的催化剂催化超声降解能力最强，苋菜红及次甲基蓝染料降解过程满足准一级方程，酸性湖蓝A染料降解过程满足准二级方程。用扫描电镜（SEM）、Mapping图、能量色散X射线光谱仪（EDX）及X射线衍射（XRD）对海螵蛸负载二氧化锰催化剂进行表征分析。     

负载纳米TiO2的纯棉抗菌织物

在室温条件下采用射频磁控溅射方法,在纯棉机织物表面沉积TiO2功能纳米结构层.利用原子力显微镜和X射线衍射仪分别分析其表面形貌和晶态结构,同时对负载纳米TiO2织物的抗菌性和耐洗性进行了初步研究.实验表明,在拟定的溅射工艺条件下,纯棉机织物表面沉积了晶粒较为均匀、粒径较小的锐钛矿型纳米TiO2功能结构层,这一功能层使负载织物呈现出优良的抗菌性能;同时负载织物具有良好的耐洗性,经30次洗涤后,其抗菌性能仍保持在很高的水平.     

TiO2/膨胀石墨复合材料的制备及表征

为了提高膨胀石墨和TiO2在污染领域的处理能力,提出了复合材料的制备方法.以硫酸为插层剂、双氧水为氧化剂,采用化学氧化法制备膨胀石墨,高温膨化得到低硫膨胀石墨,然后采用醇热法进一步制备了TiO2/膨胀石墨复合材料.采用扫描电子显微镜（SEM）和X射线衍射（XRD）对样品进行表征.以汽油为样品油,研究膨胀石墨及TiO2/膨胀石墨对汽油吸附性能.结果表明：TiO2成功负载于膨胀石墨的边缘和内壁,平均粒径为100 nm,形貌为球形.膨胀石墨对汽油的最大吸附量为40 g/g,复合材料对汽油的吸附量随着TiO2含量的增加而逐步降低.     

活性Al2O3负载Mn-Ce氧化物催化分子氧选择氧化醇类研究

以硝酸锰和硝酸铈为锰源和铈源采用湿法浸渍法制备了不同锰铈比的γ-Al2O3负载Mn-Ce氧化物催化剂．实验结果表明,该催化剂能够有效催化以分子氧为氧化剂的醇类选择氧化反应,产物以醛或酮为主,且该催化剂能够多次循环使用而不降低活性．XRD结果表明,负载在Al2O3上的锰主要是以颗粒状β-MnO2形式存在,少量铈的加入能够促进锰的分散,使负载的β-MnO2颗粒变小,从而呈现较高的催化活性．当锰铈原子比为9：1时,催化活性最高．焙烧温度影响催化剂的结构和组成,在较低的温度下（300℃以下）硝酸锰仅能部分分解为β—MnO2,而过高的温度（700℃）将使β-MnO2发生分解,从而降低催化活性．另外,本文还研究了氧分压、反应温度等动力学因素对催化反应性能的影响以及催化剂的稳定性．     

NaCl担载Fe催化CVD法合成碳洋葱

以水溶性NaCl为载体,用浸渍法制备了Fe质量分数分别为0.3%、1.6%、3.3%和5.2%的催化剂,在400℃下催化裂解乙炔合成纳米碳材料;用场发射扫描电子显微镜、高分辨透射电镜对样品进行了结构表征和分析。结果显示,利用Fe质量分数为0.3%的催化剂合成的碳洋葱颗粒直径分布在15-50 nm之间,多数在15-35 nm内。