多金核二氧化铈空心球用于硝基苯酚催化加氢（英文）

催化剂的微观结构在催化还原反应、有机物氧化反应及有机物转化反应中起着关键作用.本文利用无模板方法合成了多金核中空二氧化铈微球催化剂.将制备好的二氧化铈中空微球浸渍到一定浓度的氯金酸溶液中,然后多次洗涤除去表面吸附的氯金酸离子,最后通过硼氢化钠还原制成中空氧化铈微球包覆的多金核的核壳结构催化剂.将该核壳结构材料用于硝基苯酚加氢反应与金纳米粒子及氧化铈微球相比,多金核中空二氧化铈核壳结构表现出优越的活性和稳定性.通过这种浸渍洗涤再还原的简单方法合成的多金核二氧化铈催化剂有望应用于生物医药和能源环境等领域.     

二氧化铈纳米球的合成

使用尿素水热法合成了均匀的二氧化铈球型纳米材料.纳米球是由纳米层以及纳米颗粒所构成的核壳结构,其平均粒径为320nm,同时表面主要暴露{111}晶面.尿素水解所产生的氨气分子为纳米球状结构的形成提供了模板,而生成的碳酸根与氢氧根离子作为铈离子的沉淀剂.使用氢气程序升温还原技术表征了氧化铈纳米球材料的氧化还原能力,同时以一氧化碳氧化为探针反应研究了其催化性能.     

Pt-CeO_x/CN_xNT催化剂的高稳定性和高效氧还原性能（英文）

通过简便的方法合成出了Pt-CeO_x/CN_xNT催化剂。该催化剂以聚吡咯纳米管碳化后的含氮碳纳米管作为载体,以氧化铈作为助催化剂。实验表明,由于二氧化铈的储氧性能,也由于CN_xNT载体中氮元素的促进作用和其本身独特的一维中空结构,Pt-CeO_x/CN_xNT催化剂的氧还原性能明显高于商业Pt/C。而催化剂优秀的稳定性则源于二氧化铈对Pt纳米颗粒和载体的保护作用。     

Au@SiO2核壳纳米粒子的制备及其表面增强拉曼光谱

采用柠檬酸钠还原氯金酸法制备金溶胶, 以正硅酸乙酯(TEOS)为硅源, 氨水作催化剂, 制备以金为核, 二氧化硅为壳的核壳纳米粒子. 金纳米粒子的粒径可以通过柠檬酸钠和氯金酸的比例控制, 通过调节TEOS的量和反应的时间可以控制二氧化硅壳层的厚度. 以苯硫酚为探针分子研究了核壳结构纳米粒子的表面增强拉曼散射(SERS)效应与二氧化硅壳层厚度之间的关系. 研究结果表明, 金内核电磁场增强效应随着二氧化硅壳层厚度的增加逐渐减弱, 且其衰减速度比具有相同尺度的双金属核壳结构纳米粒子的慢. 此外, 探针分子主要以物理作用吸附在二氧化硅的表面, 可通过洗涤方法将探针分子除去, 从而可使该复合结构基底用于循环SERS分析.     

二氧化铈与氢气之间相互作用及其在炔烃选择加氢中的应用

二氧化铈因其具有较强的氧化还原性能和多变的酸碱功能而在催化领域有着广泛的应用,其可用作催化剂、改性剂或载体.虽然二氧化铈常被用于氧化反应,但由于其独特的选择性地将炔烃加氢成烯烃的能力,近年来引起了广泛的研究兴趣.氧化铈出色的加氢能力引发了新的研究热潮,以了解纯二氧化铈用作加氢催化剂的原理.本文综述了近年来氧化铈的实验和计算研究进展,重点介绍了氧化铈与氢气的相互作用和加氢反应.讨论了各种研究的重要观点,包括原位光谱/显微镜和铈在涉氢反应中的理论模型,从而阐明了氧化铈催化炔烃加氢反应能力的本质和反应机理.最后在总结和展望部分提出了进一步提高对铈基材料加氢反应机理认识和催化性能的途径.     

二氧化铈与氢气之间相互作用及其在炔烃选择加氢中的应用（英文）

二氧化铈因其具有较强的氧化还原性能和多变的酸碱功能而在催化领域有着广泛的应用,其可用作催化剂、改性剂或载体.虽然二氧化铈常被用于氧化反应,但由于其独特的选择性地将炔烃加氢成烯烃的能力,近年来引起了广泛的研究兴趣.氧化铈出色的加氢能力引发了新的研究热潮,以了解纯二氧化铈用作加氢催化剂的原理.本文综述了近年来氧化铈的实验和计算研究进展,重点介绍了氧化铈与氢气的相互作用和加氢反应.讨论了各种研究的重要观点,包括原位光谱/显微镜和铈在涉氢反应中的理论模型,从而阐明了氧化铈催化炔烃加氢反应能力的本质和反应机理.最后在总结和展望部分提出了进一步提高对铈基材料加氢反应机理认识和催化性能的途径.     

金纳米棒@碳中空胶囊的制备及催化性能

以聚吡咯为碳壳前驱体制备了金纳米棒镶嵌于碳壳内的中空胶囊.先合成羧基修饰的聚苯乙烯微球和十六烷基三甲基溴化铵稳定的金纳米棒; 再利用二者之间的静电力将金纳米棒组装在聚苯乙烯微球表面; 最后, 通过氧化聚合将聚吡咯壳包覆在聚苯乙烯@金纳米棒复合物的表面.在氮气保护下经高温煅烧, 聚吡咯壳被碳化为碳壳的同时聚苯乙烯微球分解, 从而制得金纳米棒@碳中空胶囊.在煅烧过程中, 由于碳壳的保护, 金纳米棒很好地保持了“棒状”形貌.通过调节吡咯单体的浓度, 可以控制聚吡咯壳和碳壳的厚度.金纳米棒@碳中空胶囊在以NaBH₄为还原剂还原亚甲基蓝的反应中表现出良好的催化活性.     

制备方法和助剂对贵金属铱催化剂还原性质的影响

通过应用TPR等方法研究了制备方法、焙烧温度和助剂氧化铈含量等对催化剂还原性质、吸附性能的影响 .结果表明分步浸渍法制备的催化剂活性中心比一步共浸渍法制备的催化剂的活性中心数量多 ;助剂氧化铈含量变化的催化剂中Ce含量为 1%时 ,催化剂的活性中心最多 ;共浸渍的催化剂中 ,加入助剂镁以后 ,使金属易于还原 ,加入助剂铈后 ,使贵金属难于还原     

Au@SiO_2中空微球的制备及催化性能

以天然高分子阿拉伯树胶(AG)为还原剂和稳定剂制备了金纳米粒子;将含有金纳米粒子(Au NPs)、阿拉伯树胶和氨水的溶液滴加到乙醇中形成AG-Au NPs复合胶团;利用正硅酸乙酯水解,在AG-Au NPs表面包覆二氧化硅壳层;通过简单水洗的方法得到了金纳米粒子@二氧化硅(Au@SiO_2)中空微球.采用透射电子显微镜(TEM)、X射线衍射仪(XRD)和氮气吸附实验等对Au@SiO_2中空微球进行表征.通过设计对比实验,证实阿拉伯树胶在中空结构形成过程中起到模板剂的作用.催化性能测试结果表明,所制备的Au@SiO_2中空微球在硼氢化钠还原亚甲基蓝的反应中表现出良好的催化活性和重复使用性.     

交联聚膦腈中空微球的可控制备

以分散聚合法制备的聚苯乙烯微球为模板,以六氯环三膦腈、4,4’-二羟基二苯砜为共聚单体,三乙胺为缚酸剂,室温条件下制备出了聚苯乙烯／聚膦腈（核／壳）复合微球,然后用四氢呋喃处理该复合微球,得到聚膦腈中空微球。利用红外光谱、元素分析、扫描电镜及投射电镜对所制备中空微球的结构及形貌进行了表征。结果表明,所制备聚膦腈中空微球...     

Alkylaminosilane‐Assisted Simultaneous Etching and Growth Route to Synthesise Metal Nanoparticles Encapsulated by Silica Nanorattles

An efficient and facile method to synthesise silica nanorattles with multiple noble metal (Au and Pd) cores by a simultaneous etching and growth route has been developed. In this strategy, a dual‐functional alkylaminosilane was adopted to form the middle layer of solid organic–inorganic hybrid solid‐silica spheres (HSSSs), which enabled the selective etching of the middle hybrid layer of the HSSSs and the in situ growth of metal nanoparticles (NPs) inside the cavity in a one‐step hydrothermal reaction. By adjusting the pH values of the reaction system, the metal NPs could be grown exclusively inside the silica nanorattles, resulting in a high atomic utilisation of the noble metals. The size and number of Au cores were tunable by manipulating the initial concentration of HAuCl₄. The prepared silica nanorattles with Au cores were successfully applied to the catalytic reduction of 4‐nitrophenol and showed high catalytic activity and cycle stability. Catalysts with multiple gold cores exhibited superior catalytic activity to those with a single gold core, probably because they possess smaller Au cores with greater surface area.     

Water‐dispersible Hollow Microporous Organic Network Spheres as Substrate for Electroless Deposition of Ultrafine Pd Nanoparticles with High Catalytic Activity and Recyclability

Microporous organic networks (MONs) have been considered as an ideal substrate to stabilize active metal nanoparticles. However, the development of highly water‐dispersible hollow MONs nanostructures which can serve as both the reducing agent and stabilizer is highly desirable but still challenging. Here we report a template‐assisted method to synthesize hollow microporous organic network (H‐MON) spheres using silica spheres as hard template and 1,3,5‐triethynylbenzene as the building blocks through a Glaser coupling reaction. The obtained water‐dispersible H‐MON spheres bearing sp‐ and sp²‐hybridized carbon atoms possess a highly conjugated electronic structure and show low reduction potential; thus, they can serve as a reducing agent and stabilizer for electroless deposition of highly dispersed Pd clusters to form a Pd/H‐MON spherical hollow nanocomposite. Benefitting from their high porosity, large surface area, and excellent solution dispersibility, the as‐prepared Pd/H‐MON hollow nanocomposite exhibits a high catalytic performance and recyclability toward the reduction of 4‐nitrophenol.     

A General Route to Hollow Mesoporous Rare‐Earth Silicate Nanospheres as a Catalyst Support

Hollow mesoporous structures have recently aroused intense research interest owing to their unique structural features. Herein, an effective and precisely controlled synthesis of hollow rare‐earth silicate spheres with mesoporous shells is reported for the first time, produced by a simple hydrothermal method, using silica spheres as the silica precursors. The as‐prepared hollow rare‐earth silicate spheres have large specific surface area, high pore volume, and controllable structure parameters. The results demonstrate that the selection of the chelating reagent plays critical roles in forming the hollow mesoporous structures. In addition, a simple and low‐energy‐consuming approach to synthesize highly stable and dispersive gold nanoparticle–yttrium silicate (AuNPs/YSiO) hollow nanocomposites has also been developed. The reduction of 4‐nitrophenol with AuNPs/YSiO hollow nanocomposites as the catalyst has clearly demonstrated that the hollow rare‐earth silicate spheres are good carriers for Au nanoparticles. This strategy can be extended as a general approach to prepare multifunctional yolk–shell structures with diverse compositions and morphologies simply by replacing silica spheres with silica‐coated nanocomposites.     

Gold nanoparticles stabilized by modified halloysite nanotubes for catalytic applications

A highly sustainable prototype of a flow system based on gold nanoparticles (4.2 nm) supported on thiol‐functionalized halloysite nanotubes (HNTs) was developed for catalytic applications. The catalytic performances were evaluated using the reduction of 4‐nitrophenol to 4‐aminophenol as a model system. Under the best experimental conditions (0.0001 mol%, 1.97 × 10^?8 mg of Au nanoparticles), an impressive apparent turnover frequency value up to 2 204 530 h^?1 was achieved and the halloysite‐based catalyst showed full recyclability even after ten cycles. The high catalytic activity confirms the importance of the use of HNTs as support for Au nanoparticles that can exert a synergistic effect both as medium for transfer of electrons from borohydride ions to 4‐nitrophenol and by modulating interfacial electron transfer dynamics. With the application of flow technology, the obtained heterogeneous HNT@Au catalyst was fully recovered and reused for at least one month.     

Synthesis of Hollow Mesoporous TiO2 Microspheres with Single and Double Au Nanoparticle Layers for Enhanced Visible‐Light Photocatalysis

A facile method was used to prepare hollow mesoporous TiO₂ and Au@TiO₂ spheres using polystyrene (PS) templates. Au nanoparticles (NPs) were simultaneously synthesized and attached on the surface of PS spheres by reducing AuCl₄^? ions using sodium citrate which resulted in the uniform deposition of Au NPs. The outer coating of titania via sol‐gel produced PS@Au@TiO₂ core–shell spheres. Removing the templates from these core–shell spheres through calcination produced hollow mesoporous and crystalline Au@TiO₂ spheres with Au NPs inside the TiO₂ shell in a single step. Anatase spheres with double Au NPs layers, one inside and another outside of TiO₂ shell, were also prepared. Different characterization techniques indicated the hollow mesoporous and crystalline morphology of the prepared spheres with Au NPs. Hollow anatase spheres with Au NPs indicated enhanced harvesting of visible light and therefore demonstrated efficient catalytic activity toward the degradation of organic dyes under the irradiation of visible light as compared to bare TiO₂ spheres.     

Au/ZrLa掺杂 CeO2催化剂在CO氧化反应中优异的催化活性：锆镧协同作用

在过去的25年,纳米金催化剂上 CO氧化反应得到广泛研究,但始终没有一致的结论。这是因为影响纳米金催化活性的因素很多,包括金的价态、载体的性质、氧空位、金属与载体之间的相互作用等,尤其是各影响因素之间相互牵制,增加了催化反应机理的研究难度。氧化铈载体表面氧缺陷的浓度较高,有利于活性金属组分在其表面的稳定和分散,因此氧化铈纳米晶负载的 Au催化剂受到广泛关注。此外,当 CeO2晶格中部分 Ce被化学性质不同的其它元素取代后,可以促进 CeO2晶格氧的活化,提高氧的储放能力,从而有利于催化反应进行。因此,本文采用水热法合成了组成均匀的 CeO2, CeZrOx和 CeZrLaOx三个载体,并通过沉淀-沉积法负载金。利用 X射线衍射(XRD)、拉曼光谱(Raman)、X射线光电子能谱(XPS)、高分辨透射电镜(HRTEM)、X射线吸收精细结构(XAFS)和氢气程序升温还原(H2-TPR)等技术分析了催化剂的物相结构、表面性质、形貌以及金纳米颗粒的大小和价态等性质,并结合其在 CO氧化反应中催化性能的差异,探讨影响金催化剂活性的关键因素。 XRD, TEM, HRTEM和 XAFS结果表明,三个载体上所得金纳米颗粒的平均尺寸都在2–4 nm,且分散较好; XPS结果表明,影响催化剂活性的关键因素不是金的价态,而是载体表面的活性氧物种。从Raman结果可知,掺杂后的氧化铈载体上氧空位浓度明显增加,因而催化剂活性都有所提高。 H2-TPR进一步探讨了三个载体以及负载金后其氧化还原能力的变化,结果表明,金和载体之间的相互作用可以增强载体的氧化还原性能以及表面氧空位浓度,进一步提高了催化剂活性,而负载金催化剂氧化还原性能的变化与载体的组成密切相关。由于锆的掺杂可使金与载体之间相互作用减弱,而镧则增强了二者间相互作用,因此 Au/CeZrLaOx催化剂上锆和镧的协同掺杂作用使其表面活性氧物种浓度最高,低温时表现出最高的催化活性。     

Water‐ and Organo‐Dispersible Gold Nanoparticles Supported by Using Ammonium Salts of Hyperbranched Polystyrene: Preparation and Catalysis

Gold nanoparticles (1 nm in size) stabilized by ammonium salts of hyperbranched polystyrene are prepared. Selection of the R groups provides access to both water‐ and organo‐dispersible gold nanoparticles. The resulting gold nanoparticles are subjected to studies on catalysis in solution, which include reduction of 4‐nitrophenol with sodium borohydride, aerobic oxidation of alcohols, and homocoupling of phenylboronic acid. In the reduction of 4‐nitrophenol, the catalytic activity is clearly dependent on the size of the gold nanoparticles. For the aerobic oxidation of alcohols, two types of biphasic oxidation are achieved: one is the catalyst dispersing in the aqueous phase, whereas the other is in the organic phase. The catalysts are reusable more than four times without loss of the catalytic activity. Selective synthesis of biphenyl is achieved by the homocoupling of phenylboronic acid catalyzed by organo‐dispersible gold nanoparticles.     

Constructing magnetic polyaniline/metal hybrid nanostructures using polyaniline/Fe3O4 composite hollow spheres as supports

Polyaniline (PANI)/Fe₃O₄ composite hollow spheres have been successfully synthesized in one step using sulfonated polystyrene (PS) spheres as templates. The magnetic PANI hollow spheres were used as supports for noble metal nanoparticles (NPs) such as Au and Pd. The morphology, composition and magnetic properties of the resulting products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, inductively coupled plasma (ICP) atomic spectra and vibrating sample magnetometer. The catalytic activity of magnetic PANI/Au composite shells on the oxidation of dopamine was investigated by cyclic voltammetry. The obtained results provide our product with a practical application for the detection of dopamine. On the other hand, the catalytic activity of magnetic PANI/Pd composite shells on the reduction of 4-nitroaniline was investigated by spectroscopic methods and compared with Pd/C catalyst which was already widely used in industrial production.     

CeO2 nanorods and gold nanocrystals supported on CeO2 nanorods as catalyst

The formation mechanism of uniform CeO2 structure at the nanometer scale via a wet-chemical reaction is of great interest in fundamental study as well as a variety of applications. In this work, large-scale well-crystallized CeO2 nanorods with uniform diameters in the range of 20-30 nm and lengths up to tens of micrometers are first synthesized through a hydrothermal synthetic route in 5 M KOH solution at 180 degrees C for 45 h without any templates and surfactants. The nanorod formation involves dehydration of CeO2 nanoparticles and orientation growth along the 110 direction in KOH solution. Subsequently, gold nanoparticles with crystallite sizes between 10 and 20 nm are loaded on the surface of CeO2 nanorods using HAuCl4 solution as the gold source and NaBH4 solution as a reducing agent. The synthesized Au/CeO2 nanorods demonstrate a higher catalytic activity in CO oxidation than the pure CeO2 nanorods.     

Controlled synthesis of novel cyanopropyl polysilsesquioxane hollow spheres loaded with highly dispersed Au nanoparticles for catalytic applications

The design and synthesis of novel cyanopropyl polysilsesquioxane hollow spheres lead to production of a highly active and stable catalyst in the reduction of 4-nitrophenol catalyzed by Au nanoparticles.