铜纳米粒子负载于钴纳米片的双金属催化剂催化CO选择性加氢

使用赖氨酸作为表面活性剂模板, 合成了Cu纳米粒子负载于Co纳米片的双金属催化剂Cu/Co. 与常规的Cu-Co双金属纳米颗粒催化剂相比, Cu/Co催化剂对CO选择性加氢反应表现出特殊的结构效应, 提高了CO转化率和高级醇选择性, 降低了甲烷选择性. Cu/Co催化剂中, Cu(111)面与Co(100)面相互作用的功能化界面有利于深入研究金属-金属的相互作用. 这种双金属催化剂可以将模型催化剂和现实催化应用联系起来, 将有助于获得对合成气转化制高级醇反应机理的本质认识.     

SiO2负载的Au-Ni双金属催化剂在乙炔选择加氢反应中的应用

负载型Au催化剂在乙炔选择加氢反应中表现出很高的乙烯选择性,但其转化率相对较低.通过添加第二种金属如Pd,Fe,Ag和Cu等,制备双金属催化剂是提高其在加氢反应中催化活性的一种非常有效的手段.其中Au-Pd双金属催化剂是最受关注的体系之一,Pd的加入可以非常显著地提高其催化乙炔选择加氢反应的活性.据文献报道,与Pd同一主族的Ni也具有较好的加氢活性.尽管与Pd相比,Ni很难与Au形成合金,但目前已有Au-Ni双金属催化剂在多种反应中表现出协同效应的报道,如水气变换、CO氧化以及芳香硝基化合物选择加氢等.因此,向Au催化剂中添加Ni也可能提高催化剂在乙炔选择加氢反应中的催化活性.因此,我们采用两步法制备了一系列SiO2负载的具有不同Ni:Au原子比的Au-Ni双金属催化剂,并将其用于乙炔选择加氢反应,发现Au-Ni双金属催化剂在该反应中表现出了显著的协同效应,其活性明显优于相应单金属催化剂的活性.尽管其乙烯选择性略低于单金属Au催化剂,但明显高于单金属Ni催化剂.通过调节还原温度和/或Ni:Au的比例,对催化剂的性能进行了优化.结果显示,当Ni:Au=0.5时,催化剂表现出最优的综合性能,即兼具较高的乙炔转化率和乙烯选择性.为了研究Au-Ni双金属催化剂中金属纳米粒子的结构、组成以及Au-Ni之间的相互作用,我们对催化剂进行了X射线衍射(XRD)、高分辨透射电镜(HRTEM)、能量散射谱(EDS)以及原位红外光谱(DRIFTS)表征.XRD和TEM结果显示,催化剂中的Au-Ni双金属纳米粒子都具有高分散和粒径均匀的特点.通过EDS分析,发现在Au-Ni双金属催化剂中的单个金属纳米粒子同时含有Au和Ni两种元素,尽管每个纳米粒子中Ni:Au的比例有差异.HRTEM结果发现,Au-Ni双金属纳米粒子的晶格间距介于Au(111)和Ni(111)的晶面间距之间,说明在Au-Ni双金属催化剂中有Au-Ni合金形成.原位DRIFTS结果显示,在Au-Ni双金属催化剂中,Au的存在促进了Ni的还原,说明Au与Ni之间存在紧密的相互作用.综上可见,Au和Ni在乙炔选择加氢反应中所表现出的协同效应主要归功于Au-Ni合金的形成,其中金属态Ni起主要的活性作用,而Au的存在则提高了催化剂的乙烯选择性.     

SiO_2负载的Au-Ni双金属催化剂在乙炔选择加氢反应中的应用（英文）

负载型Au催化剂在乙炔选择加氢反应中表现出很高的乙烯选择性,但其转化率相对较低.通过添加第二种金属如Pd,Fe,Ag和Cu等,制备双金属催化剂是提高其在加氢反应中催化活性的一种非常有效的手段.其中Au-Pd双金属催化剂是最受关注的体系之一,Pd的加入可以非常显著地提高其催化乙炔选择加氢反应的活性.据文献报道,与Pd同一主族的Ni也具有较好的加氢活性.尽管与Pd相比,Ni很难与Au形成合金,但目前已有Au-Ni双金属催化剂在多种反应中表现出协同效应的报道,如水气变换、CO氧化以及芳香硝基化合物选择加氢等.因此,向Au催化剂中添加Ni也可能提高催化剂在乙炔选择加氢反应中的催化活性.因此,我们采用两步法制备了一系列Si O2负载的具有不同Ni:Au原子比的Au-Ni双金属催化剂,并将其用于乙炔选择加氢反应,发现Au-Ni双金属催化剂在该反应中表现出了显著的协同效应,其活性明显优于相应单金属催化剂的活性.尽管其乙烯选择性略低于单金属Au催化剂,但明显高于单金属Ni催化剂.通过调节还原温度和/或Ni:Au的比例,对催化剂的性能进行了优化.结果显示,当Ni:Au=0.5时,催化剂表现出最优的综合性能,即兼具较高的乙炔转化率和乙烯选择性.为了研究Au-Ni双金属催化剂中金属纳米粒子的结构、组成以及Au-Ni之间的相互作用,我们对催化剂进行了X射线衍射(XRD)、高分辨透射电镜(HRTEM)、能量散射谱(EDS)以及原位红外光谱(DRIFTS)表征.XRD和TEM结果显示,催化剂中的Au-Ni双金属纳米粒子都具有高分散和粒径均匀的特点.通过EDS分析,发现在Au-Ni双金属催化剂中的单个金属纳米粒子同时含有Au和Ni两种元素,尽管每个纳米粒子中Ni:Au的比例有差异.HRTEM结果发现,Au-Ni双金属纳米粒子的晶格间距介于Au(111)和Ni(111)的晶面间距之间,说明在Au-Ni双金属催化剂中有Au-Ni合金形成.原位DRIFTS结果显示,在Au-Ni双金属催化剂中,Au的存在促进了Ni的还原,说明Au与Ni之间存在紧密的相互作用.综上可见,Au和Ni在乙炔选择加氢反应中所表现出的协同效应主要归功于Au-Ni合金的形成,其中金属态Ni起主要的活性作用,而Au的存在则提高了催化剂的乙烯选择性.     

高利用率多壁碳纳米管负载金铂合金纳米粒子催化剂在碱性溶液中的甲醇电催化氧化性能研究

使用乙二醇还原法合成了一系列高利用率多壁碳纳米管负载的金铂双金属纳米粒子电催化剂,在碱性溶液中由循环伏安和计时电流法测试该AuPt催化剂对于甲醇氧化反应的电催化活性.透射电子显微镜、X射线衍射与X射线能谱观测催化剂形貌,表征催化剂结构.结果表明,金铂双金属纳米粒子均匀分散在碳纳米管上,催化剂具有良好甲醇电氧化性能.实验表明Au/Pt/MWCNTs比为10∶8∶32(bymass)时,该催化剂具有最高甲醇电氧化峰电流密度与最负起始氧化电位.     

Pd/Ni异结构纳米催化剂的制备及其对甲酸氧化的电催化

通过两步还原法制备了Pd/Ni双金属催化剂.由于金属Pd原子在先行还原的Ni纳米粒子表面的外延生长以及其在Ni表面及Pd表面生长表现出的吉布斯自由能差异,最终导致了异结构Pd/Ni纳米粒子的形成.高分辨电子透射显微镜结果证实了异结构的存在,然而X射线衍射测量表明Pd/Ni纳米粒子具有类似于Pd的面心立方结构.制备的Pd/Ni纳米粒子与同等条件下合成的Pd纳米粒子相比对甲酸氧化呈现了更高的电催化活性,而且电催化稳定性也要明显优于纯Pd纳米粒子,证明Pd/Ni双金属催化剂是可选的直接甲酸燃料电池阳极催化剂.双金属催化剂对甲酸氧化电催化活性和稳定性增强可能是Ni原子的修饰改变了Pd粒子表面配位不饱和原子的电子结构所致.     

金属纳米粒子/聚合物体系的稳定性及其机理

金属纳米粒子由于其小的尺寸和大的比表面积等特点,使其具有独特的热性能、电性能、磁性能和光性能,以及很强的团聚趋势.因此金属纳米粒子是否被稳定在纳米尺度内,是它们能否表现出独特性能的关键.本文综述了非离子聚合物、聚电解质、两亲聚合物、双亲水聚合物、树状聚合物对金属纳米粒子的稳定作用及其稳定机理的研究进展.     

纳米粒子毛细管电色谱技术及其应用

纳米粒子以其较大的比表面积、良好的生物相容性而被广泛应用于分离科学领域. 纳米粒子毛细管电色谱(NPCEC)是纳米材料技术与毛细管电泳/电色谱(CE/CEC)技术相结合的产物.NPCEC技术是将不同基质的功能化纳米粒子加入电泳的运行缓冲液中,纳米粒子不仅可以通过动态吸附于毛细管壁而改变(或逆转)电渗流,还可作为准固定相(PSPs)参与样品在柱内的分配和保留,从而提高柱效和改善分离的选择性.该技术因无需填充和柱塞制备等步骤而日益受到关注.此外,NPCEC技术还可实现良好的柱更换,避免了进行复杂样品分析时所造成的柱污染.该文重点讨论在NPCEC实验中常用的几种纳米粒子的合成及应用,包括聚合物纳米粒子、二氧化硅纳米粒子、金纳米粒子、碳纳米管和树状聚合物,并对其发展前景进行了展望.     

贵金属固体催化剂的纳米结构及催化性能

 综述了贵金属催化剂纳米结构的形成和制备方法,以及催化活性与纳米粒子尺寸的关系. 还以负载型双金属催化剂为例,介绍了催化剂中的短程有序结构.     

Pt/Ni双金属纳米溶胶的制备及催化制氢性能

采用化学共还原法制备了聚乙烯吡咯烷酮(PVP)稳定的Pt/Ni双金属纳米溶胶.采用紫外-可见光谱(UV-Vis)、透射电子显微镜(TEM)对所合成的Pt/Ni双金属纳米溶胶进行了表征, 并系统研究了PVP用量、还原剂用量和浓度、双金属比例对该双金属纳米溶胶催化剂催化性能的影响.结果表明, 所制备的双金属纳米溶胶的平均粒径在2.0 nm左右, Pt/Ni双金属纳米溶胶的催化活性比Pt及Ni单金属纳米溶胶的高, 当Pt/Ni摩尔比为1:4时, 纳米溶胶的催化活性最高, 其活性值为16640 mol_H2·mol_Pt^-1·h^-1.所制备的Pt/Ni双金属纳米溶胶催化剂具有很好的耐久性, 5次催化实验后该催化剂仍保持较高的催化活性.该双金属纳米溶胶催化NaBH₄水解反应的活化能为48 kJ/mol.     

金属纳米粒子/聚合物体系的稳定性及其机理

金属纳米粒子由于其小的尺寸和大的比表面积等特点,使其具有独特的热性能、电性能、磁性能和光性能,以及很强的团聚趋势。因此金属纳米粒子是否被稳定在纳米尺度内,是它们能否表现出独特性能的关键。本文综述了非离子聚合物、聚电解质、两亲聚合物、双亲水聚合物、树状聚合物对金属纳米粒子的稳定作用及其稳定机理的研究进展。     

Bimetallic dendrimer-encapsulated nanoparticles as catalysts: a review of the research advances

Bimetallic dendrimer-encapsulated nanoparticles (DENs) are important materials, because they have demonstrated improvement in performance compared to the monometallic DENs in many systems when they are used as catalysts. This tutorial review focuses on the recent research advances in bimetallic DENs with respect to their synthesis, characterization, and applications as catalysts. Bimetallic DENs can be made mainly via three routes: co-complexation, sequential loading, and partial displacement. The research in bimetallic DENs has been significantly promoted by the advancement of characterization instruments. The performances of bimetallic DENs as homogeneous and heterogeneous catalysts in organic synthesis have been compared with both monometallic DENs and their physical mixtures. It is concluded that the synergistic electronic effect in bimetallic nanoparticles enhances their catalytic activities.     

Synthesis, characterization, and structure-selective extraction of 1-3-nm diameter AuAg dendrimer-encapsulated bimetallic nanoparticles

The synthesis and characterization of 1-3-nm diameter, structurally well-defined, bimetallic AuAg dendrimer-encapsulated nanoparticles (DENs) are reported. Three different bimetallic structures were examined: AuAg alloys synthesized by cocomplexation and subsequent reduction of dendrimer-encapsulated Au3+ and Ag+ and core/shell [Au](Ag) and [AuAg alloy](Ag) structures (for structured materials, brackets indicate the core metal and parentheses indicate the shell metal) synthesized by a sequential loading method. Depending on the shell metal and its oxidation state, the AuAg nanoparticles can be extracted from the dendrimer into an organic phase using different surfactants. This provides a means for analyzing the composition of the shell. UV-vis, TEM, and single-particle X-ray energy dispersive spectroscopy (EDS) were used to characterize the bimetallic DENs before and after extraction and show that the extraction step does not alter the size or composition of the bimetallic nanoparticles.     

Synthesis and Characterization of Dendrimer‐Encapsulated Bimetallic Core‐Shell PdPt Nanoparticles

Using a successive method, PAMAM dendrimer‐encapsulated bimetallic PdPt nanoparticles have been successfully prepared with core‐shell structures (Pd@Pt DENs). Evidenced by UV‐vis spectra, high resolution transmission electron microscopy, and X‐ray energy dispersive spectroscopy (EDS), the obtained Pd@Pt DENs are monodispersed and located inside the cavity of dendrimers, and they show a different structure from monometallic Pt or Pd and alloy PdPt DENs. The core‐shell structure of Pd@Pt DENs is further confirmed by infrared measurements with carbon monoxide (IR‐CO) probe. In order to prepare Pd@Pt DENs, a required Pd/Pt ratio of 1:2 is determined for the Pt shell to cover the Pd core completely. Finally, a mechanism for the formation of Pd@Pt DENs is proposed.     

Synthesis, characterization, and surface immobilization of platinum and palladium nanoparticles encapsulated within amine-terminated poly(amidoamine) dendrimers

Platinum and palladium dendrimer-encapsulated nanoparticles (DENs) were prepared within commercially available, fourth-generation, amine-terminated, poly(amidoamine) dendrimers (G4-NH2). The synthesis is carried out by selectively encapsulating metal complexes within the dendrimer and then reducing the resulting composite. Intradendrimer complexation requires control over the solution pH to prevent attachment of the metal complexes to primary amine groups on the dendrimer periphery. That is, the surface primary amines of the dendrimer must be selectively protonated in the presence of the interior tertiary amines. The metal-ion encapsulation and reduction processes were characterized by UV-vis spectroscopy. Forty-atom Pt and Pd DENs were examined by high-resolution transmission electron microscopy, which showed that the mean particle sizes were 1.4 and 1.5 nm, respectively, and that both were nearly monodisperse (standard deviation = 0.3 nm). The free amine groups on the dendrimer surface were used to link Pd DENs to monolithic Au surfaces via an intermediate self-assembled monolayer adhesion layer.     

Bimetallic Dendrimer-encapsulated Nanoparticle Catalysts

Bimetallic dendrimer-encapsulated nanoparticles (DENs) have been receiving a significant amount of attention due to their promising properties, unique characteristics, and novel applications in catalysis and other advanced “nano-” science and technology areas. Bimetallic DENs catalysts, as reviewed here, have shown a higher catalytic activity than the monometallic DENs in various catalytic systems. In this review, a general background for the dendrimer is first presented, which is then followed by an introduction of two major routes that are most often adopted in the preparation of dendrimers: divergent method and convergent method. Then, recent research advances in the synthesis, characterization, and catalytic applications of bimetallic DENs are summarized and highlighted in this article. A conclusion is then provided.     

非共价键自组装制备聚对苯撑乙炔/聚丙烯酸水溶性荧光纳米粒子及其光物理行为研究

通过功能化聚对苯撑乙炔(含羟基与氨基)和聚丙烯酸之间的非共价键自组装制备了一系列含共轭聚合物的水溶性荧光纳米粒子, 并进行了相关结构和光学性质表征. 研究表明, 纳米粒子的大小和聚丙烯酸/聚对苯撑乙炔质量比直接相关. 光物理性质研究表明, 形成水溶性纳米粒子后, 疏水的聚苯撑乙炔链在纳米粒子中易于形成π-链间聚集, 其光物理性质与其在薄膜态时相似.     

Effect of particle size on the kinetics of the electrocatalytic oxygen reduction reaction catalyzed by Pt dendrimer-encapsulated nanoparticles

Platinum dendrimer-encapsulated nanoparticles (DENs) containing an average of 55, 100, 147, 200, and 240 atoms were prepared within sixth-generation, hydroxyl-terminated, poly(amidoamine) dendrimers. These DENs were immobilized on glassy carbon electrodes, and the effect of particle size on the kinetics of the oxygen reduction reaction (ORR) was quantitatively evaluated using rotating disk voltammetry. The total areas of the Pt DENs were determined by electrochemical CO stripping and hydrogen desorption, and the results were found to be in reasonable agreement with calculated values. The largest particles exhibited the highest specific activities for the ORR.     

Hydrophobic dendrimers as templates for au nanoparticles

We report the synthesis, characterization, and extraction of Au dendrimer-encapsulated nanoparticles (DENs) prepared in organic solvents. DENs composed of 31 and 55 Au atoms were prepared using organic solvents and poly(amidoamine) (PAMAM) dendrimer templates modified on their periphery with dodecyl groups. The spectral and microscopic properties of the resulting materials were identical to those prepared using water-soluble PAMAM dendrimers. It was possible to extract the organic-soluble DENs into water using the water-soluble thiols tiopronin and glutathione. The properties of the resulting monolayer-protected clusters were nearly identical to those of the precursor DENs. A mechanistic model for the extraction process is discussed. The synthetic methodology reported here provides a convenient method for preparing DENs of non noble metals such as Ni and Fe.     

Photo-Oxidative Degradation of Poly(vinyl Chloride) Based Nanocomposites Under Ultraviolet Irradiation

The poly(vinyl chloride) based nanocomposites with 3.0% weight content of the photo-active zinc oxide (ZnO) nanoparticles or the photo-inert calcium carbonate (CaCO₃) nanoparticles was prepared by the solution mixing method, respectively. Their photo-oxidative degradation under ultraviolet irradiation (365 nm) at room temperature were compared with the pure poly(vinyl chloride) via Fourier transform infrared spectroscopy, Thermogravimetric analysis and x-ray photoelectron spectroscopy analyses. The results showed that the photo-inert calcium carbonate (CaCO₃) nanoparticles hampered the photo-degradation of poly(vinyl chloride), whereas the photoactive zinc oxide (ZnO) nanoparticles accelerated the photodegradation of poly(vinyl chloride). Furthermore, the ZnO nanoparticles also favored the crosslinking reaction of the dehydrochlorinated poly(vinyl chloride).     

不同代数超支化聚胺酯的制备及其在钕纳米粒子制备中的应用

以N，N-二羟乙基-3-胺基丙酸甲酯单体和季戊四醇（核）为原料，采用“准一步法”合成了具有端羟基的超支化聚胺酯（HPAE）。采用凝胶色谱、红外光谱、核磁共振和热重分析等对其进行了结构表征及性能探究。再以HPAE封装稀土粒子钕（Nd），制备出Nd复合纳米粒子，透射电镜（TEM）分析结果表明：随着HPAE代数增大，Nd纳米颗粒粒径越均匀，分散度越好。