薄壁中孔碳材料的精细控制合成

利用γ-氧化铝为模板, 精细控制合成了一系列具有不同孔径的中孔碳材料. 在优化的条件下, 所得的碳材料具有孔径分布窄、比表面积高(>1000 m²·g^-1)、孔容大(最高3.82 cm³·g^-1)、中孔率高(>99%)的特点, 并且孔壁厚度仅有1-2个石墨层. 选用了三种不同来源的氧化铝为模板, 考察了模板与所得碳材料织构的相关性, 并提出用无序模板可控制备碳材料的机理. 即在碳包覆氧化铝的复合物前体中, 若碳层完整覆盖氧化铝表面并且足够强韧, 则所得碳材料可近似复制模板的孔结构, 并且碳材料的孔一部分由去除模板所生成, 另一部分来源于模板原有的孔. 据此模型对所得碳材料的孔容进行了理论计算, 其结果有力支持了上述机理.     

尿素在斜发沸石上的自发单层分散

我们发现多种氧化物和盐类可以在载体表面自发单层分散,并存在分散阈值[1].近几年来又探讨了有机物在载体上的分散[2],验证了这一现象的普遍性.尿素是一种特殊物质,作为第一个人工合成的有机物,它同时具有有机物和无机物的性质.因此研究尿素在载体上的分散行为对于关联有机物和无机物的分散性质有重要的意义,也是对自发单层分散理论的充实.而且,尿素作为化肥工业的支柱,研究它的分散状态和分散性质,可以为制备缓释型化肥,提高化肥利用率,减少环境污染提供新的思路.1　实验部分1.1　样品制备　　载体为我国北方产斜发沸石,尿素由北京化工厂生…     

热解蔗糖/γ-氧化铝制备碳均匀覆盖的碳/氧化铝复合材料

碳/氧化铝复合材料（CCA）作为催化剂载体或吸附剂具有广泛用途.在文献报道中,大部分的碳-氧化铝复合材料是通过热解气相碳氢化合物制得的,这样在氧化铝表面覆盖的碳通常是不均匀的.本文提出了一个操作简便,且重复性高的新方法来制备碳均匀覆盖的碳/氧化铝复合材料——热解均匀分散在氧化铝表面的蔗糖.在这种复合材料中,碳层厚度可控制为一个石墨单层的厚度,且碳的覆盖度及层数可以通过改变浸渍的蔗糖量及浸渍次数来进行调控.     

介孔碳基钴镍氧化物的电化学电容性能

以介孔碳CMK-3为载体,利用CMK-3表面缺陷作形核中心,应用前驱体化学液相共沉淀法制备新型的Co0.25Ni0.75氧化物/CMK-3复合材料.X射线衍射（XRD）分析及扫描电子显微镜（SEM）形貌观察表明该材料主要呈现弱结晶态结构,其中Co-Ni氧化物纳米片交错成空间网络并包覆在介孔碳表面.BET测试表明该材料孔径分布在3~4 nm之间,且高分散、疏松多孔,具有良好的OH-离子传递特性.循环伏安和恒流充放电测试表明,该材料有高的电化学活性, 在5 mA/cm2电流密度下,Co0.25Ni0.75氧化物（92%）/C比电容达1781F/g.     

碳/氧化物复合物中碳层对氧化物相变的影响

碳/氧化铝(氧化钛)复合物具有独特的物理化学性质,在吸附和催化过程中有广泛应用.复合物中碳层对氧化物的相变有重要影响.在高温下通氧气焙烧碳/γ-Al2O3复合物可使γ-Al2O3迅速转变为α-Al2O3;而在惰性气氛中,碳层可显著抑制氧化铝的相变与烧结.碳/氧化钛体系中,碳层可明显提高氧化钛在惰性气氛中的热稳定性,在800℃以下碳层能有效阻止锐钛矿相向金红石相的转变;在含氧气氛中控制焙烧条件可将碳层完全除去而基本不影响氧化钛的物相组成及织构.因此,碳层可作为一种特殊的表面修饰剂,既可在高温下抑制氧化物的相变,又可避免在氧化物中引入掺杂元素.     

用于锂离子电池正极材料的分级孔碳/2,5-二巯基-1,3,4-噻二唑/聚噻吩三元复合物

采用酚醛树脂为碳源, 纳米碳酸钙为二次成孔剂, 通过煅烧、刻蚀、KOH活化等工艺制备出活化分级孔碳(aHPC). 在此基础上, 以aHPC为模板, 通过溶液浸渍制得活化分级孔碳/2,5-二巯基-1,3,4-噻二唑(aHPC/DMcT)复合物, 然后运用氧化聚合法将聚(3,4-乙烯二氧噻吩)—聚苯乙烯磺酸(PEDOT-PSS)包覆在其表面制备出aHPC/DMcT/PEDOT-PSS复合物. 并运用傅里叶变换红外(FTIR)光谱、X射线衍射(XRD)、场发射扫描电镜(FESEM)、透射电镜(TEM)和电化学测试等手段对所得复合材料的结构、形貌及电化学性能进行表征. 结果显示, KOH活化后, aHPC孔道内的官能基团含量增加了, 使得DMcT的负载量增大(52%), 且DMcT几乎全部进入到aHPC孔道内. aHPC/DMcT复合物的首次放电容量为236 mAh·g^-1, 循环20次后放电比容量仅为65mAh·g^-1. 而aHPC/DMcT/PEDOT-PSS复合物的表面包覆一层PEDOT-PSS导电薄膜, 其首次放电容量高达281 mAh·g^-1, 20次后的放电比容量为138 mAh·g^-1,容量保持率达49.1%.     

二氧化碳膨胀乙醇体系中碳基金属复合物的合成及其催化和电化学性能(英文)

与块体材料相比,功能复合材料表现了更加优异的性能,而且比其中任何单一组分的性能都好,因此在催化、锂离子电池等领域得以广泛研究.通常情况下,在复合材料的制备中金属或金属氧化物粒子要求能够以足够小的粒径在基底上均匀分散,并实现活性组分负载量的可控.据报道,很多方法可以将金属(或氧化物)活性组分引入到载体之中,比如水热/溶剂热、水解、热分解、化学气相沉积等,但这些方法均存在如下缺点.第一,为了获得满意的负载量和可控包覆,碳基底需要预氧化处理使其表面含有丰富的含氧官能团.例如,由于碳纳米管自身的相容性和加工性较差,需要硝酸预氧化处理;石墨烯也需要预处理为石墨烯氧化物然后再进行第二组分的负载.但是,剧烈的氧化处理条件不可避免地造成对碳sp~2结构和电子特性的破坏,并且增加了繁杂的后续处理过程.第二,金属组分前驱体在基底上负载不完全,易形成自由粒子聚集在溶液中,从而降低活性组分的有效利用.第三,传统方法中由于使用水、乙醇等表面张力大的极性溶剂,导致粒子结晶再生长,形成的颗粒尺寸大,对催化剂会降低活性表面积及催化效率;对于电池材料会增加电极/电解液的接触面积,增加锂离子的扩散距离及电池充电过程的内部应力.而且,有机溶剂由于粘度大,不利于金属纳米粒子在基底上的均匀分散及合成过程的绿色化.因此,我们利用资源丰富,廉价的二氧化碳作为绿色溶剂,研究了二氧化碳膨胀的乙醇体系中金属(氧化物)纳米粒子在碳基底上均匀负载的方法.由于超临界二氧化碳具有独特的低粘度、"零"表面张力、高扩散能力、以及物性参数随温度和压力可调等特点,可以使金属(氧化物)前驱体不受液体毛细作用的限制在孔道中快速、均一地分散,保证孔结构稳定,对多孔复合材料的加工和制备表现了巨大的优势.同时,超临界二氧化碳的抗溶剂能力也能够有效降低乙醇和水引起的溶剂效应,从而降低纳米粒子之间的聚集.此外,通过改变前驱体的浓度可以精确调控表面组分的负载量.更重要的是,碳基底可以直接利用制备碳基复合材料,无需任何预处理及表面活性剂参与,避免了前处理对基底的形貌和电子特性的破坏.本综述首先介绍了超临界二氧化碳膨胀乙醇体系的属性,讨论了碳基复合材料在该体系中的形成机理.然后分别介绍了零维碳球、一维碳纳米管、二维石墨烯、三维多孔碳材料作为基底形成的一系列金属(氧化物)复合材料,及这些材料在催化和锂离子电池领域中的应用.最后,对超临界二氧化碳沉积方法的应用进行了总结和展望.     

某些有机物在氧化物载体表面的自发单层分散

自发单层分散原理已在载负型催化剂制备、再生等方面得到越来越广泛的应用[1，2]．许多氧化物和盐类可以在载体表面形成单层分散或亚单层分散．有些分散物与载体混合后在低于其熔点的温度下处理，就可以自发分散到载体表面[1，3]．这一现象通过XRD、LRS、XPS、SIMS、ISS、EXAFS     

原位限域合成介孔碳负载四氧化三铁纳米颗粒

利用废弃蟹壳做模板制备的具有均一孔道结构的介孔碳材料做载体,在孔道内限域原位合成四氧化三铁氧化物纳米颗粒。 通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线衍射(XRD)表征了材料的结构和性能。 结果表明,孔道结构呈整体式结构,孔直径在40~50 nm,长50~200 μm。 纳米颗粒为四氧化三铁,粒径在10 nm左右,尺寸单分散性好,可均匀分散在介孔孔道内。 该方法工艺路线简单,绿色环保。     

钛锆复合氧化物载体的制备、物化性质及在催化反应中的应用

 TiO2-ZrO2复合氧化物具有比TiO2和ZrO2更高的比表面积、更好的热稳定性和更强的表面酸碱性,作为催化剂载体已引起很大的研究兴趣并得到了重要的应用. 本文主要介绍了TiO2-ZrO2复合氧化物载体的制备方法以及织构、结构和表面酸碱性等物化性质,并对其在催化反应中的应用进行了综述.     

以MOFs为前驱体的多孔金属氧化物催化剂研究进展

多孔金属氧化物具有高比表面积、大孔径、特殊的形貌和结构特性,广泛应用于催化、锂离子电池、太阳能电池、气敏传感器等领域。金属有机骨架材料(MOFs)是一类具有周期性网络结构的新型多孔晶体材料,在气体存储、气体分离、催化等领域具有重要的应用价值。近年来,以MOFs为前驱体制备多孔碳和多孔金属氧化物成为MOFs应用领域一个新的研究热点。本文主要综述了以MOFs为前驱体制备的多孔金属氧化物和多孔金属氧化物/碳复合物在CO氧化、催化产氢、异丁烷脱氢、环已烯氧化、醇直接氧化为酯、醛氧化酰胺化反应、光催化降解有机物和氧还原反应等方面的应用。     

Preparation and characterization of supports with a synthesized layer of catalytic filamentous carbon: IV. Synthesis of carbon nanofibers on a Co/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst

A comparative study of the synthesis of carbon layers, including catalytic filamentous carbon, on the surface of various alumina modifications was made. The synthesis was performed by the pyrolysis of alkanes (a propane-butane mixture) on Co/Al₂O₃ supported catalysts. The texture characteristics (specific surface area and pore structure) of the starting supports and adsorbents with a synthesized carbon layer were studied. The surface morphology of Co/Al₂O₃ catalysts and the synthesized carbon deposits was studied by scanning electron microscopy. It was found that carbon nanofibers were formed only on the catalysts prepared by the homogeneous precipitation of Co compounds onto the surface of macroporous α-Al₂O₃, whereas carbon deposits on mesoporous aluminum oxides did not exhibit a pronounced fibrous structure. The applicability of C/Co/Al₂O₃ carbon-containing adsorbents to the immobilization of the nitrile hydratase enzyme and the preparation of a biocatalyst for acrylonitrile hydration to acrylamide was considered.     

“嵌入模型”在γ-Al2O3负载单组分和双组分金属氧化物催化剂中的应用

探讨负载型金属氧化物催化剂的表面组分与载体之间的相互作用, 有助于理解相关催化剂的催化作用本质. 近年来, 我们对单组分CuO以及双组分CuO-Mn₂O₃, CuO-CoO等金属氧化物在γ-Al₂O₃载体表面的分散行为和存在状态, 及其物理化学性质和催化性能(CO+O₂和NO+CO模型反应)进行了研究. 结果表明, 这些金属氧化物在γ-Al₂O₃载体表面的分散行为和所得负载型催化剂样品的一些物理化学性质及其催化性能均可参照“嵌入模型”来解释. 在此基础上, 我们讨论了这些样品的“组成-结构-性质”间的关系, 并针对表面负载双组分金属氧化物样品提出了表面协同氧空位参与的NO+CO反应机理.     

Preparation and performance of polyvinyl alcohol-based activated carbon as electrode material in both aqueous and organic electrolytes

Porous carbon materials with high surface area and different pore structure have been successfully prepared by phenolic resin combined with polyvinyl alcohol (PVA) and KOH as activation agents. The surface morphology, structure, and specific surface area of the carbon materials were studied by scanning electron microscopy, X-ray diffraction, and nitrogen sorption measurement, respectively. Furthermore, the effects of specific surface area, pore structure, and electrolyte on electrochemical properties were investigated by galvanostatic charge–discharge measurement. The results show that KOH–PVA-activated carbon materials display specific capacitance as high as 218 F?g^?1 in 30 wt.% KOH aqueous electrolyte, 147 F?g^?1 in 1 M LiPF₆/(ethylene carbonate (EC) + dimethyl carbonate) (1:1?v/v), and 115 F?g^?1 in 1 M Et₃MeNBF₄/propylene carbonate organic electrolyte, respectively. In addition, the carbon materials demonstrate long-term cycle stability, especially the AK3P-0.30 in aqueous electrolyte and the AK2P-0.30 with excellent rate capability in organic electrolyte. These reveal that the existence of a micro-mesoporous structure of activated carbon is beneficial to store energy in an aqueous supercapacitor and broad pore size distribution of activated carbon is favorable to energy storage in an organic supercapacitor. The carbon materials with pore size distribution in different ranges improve the electrochemical performance of supercapacitor in different electrolytes. A new pore-expand agent (PVA combining with KOH) was used to obtain porous carbons with enhanced properties for supercapacitor.     

Biomolecule-Assisted Synthesis of Hierarchical Multilayered Boehmite and Alumina Nanosheets for Enhanced Molybdenum Adsorption

The effective utilization of various biomolecules for creating a series of mesoporous boehmite (γ-AlOOH) and gamma-alumina (γ-Al₂O₃) nanosheets with unique hierarchical multilayered structures is demonstrated. The nature and concentration of the biomolecules strongly influence the degree of the crystallinity, the morphology, and the textural properties of the resulting γ-AlOOH and γ-Al₂O₃ nanosheets, allowing for easy tuning. The hierarchical γ-AlOOH and γ-Al₂O₃ multilayered nanosheets synthesized by using biomolecules exhibit enhanced crystallinity, improved particle separation, and well-defined multilayered structures compared to those obtained without biomolecules. More impressively, these γ-AlOOH and γ-Al₂O₃ nanosheets possess high surface areas up to 425 and 371 m² g⁻¹, respectively, due to their mesoporous nature and hierarchical multilayered structure. When employed for molybdenum adsorption toward medical radioisotope production, the hierarchical γ-Al₂O₃ multilayered nanosheets exhibit Mo adsorption capacities of 33.1–40.8 mg g⁻¹. The Mo adsorption performance of these materials is influenced by the synergistic combination of the crystallinity, the surface area, and the pore volume. It is expected that the proposed biomolecule-assisted strategy may be expanded for the creation of other 3D mesoporous oxides in the future.     

Preparation and characterization of supports with a synthesized layer of catalytic filamentous carbon: III. Synthesis of carbon nanofibers on nickel supported onto aluminum oxide

The synthesis of catalytic filamentous carbon (CFC) on catalysts prepared by supporting Ni²⁺ compounds onto the surface of various alumina modifications (macroporous α-Al₂O₃ and mesoporous ?-Al₂O₃ and δ-Al₂O₃) using two procedures (impregnation and homogeneous precipitation) was studied. The texture characteristics (specific surface area and pore structure) of the parent supports and adsorbents with a CFC layer were compared. The effect of the supporting procedure on the surface morphology of Ni/Al₂O₃ catalysts and the synthesized CFC layer was studied by scanning electron microscopy. It was found that the carbon yield on a macroporous catalyst prepared by homogeneous precipitation was higher than that on a catalyst prepared by impregnation by a factor of ～2. The CFC layer exhibited a mesoporous structure because of a chaotic interlacing of carbon nanofibers, and the synthesis of CFC on macroporous supports resulted in the formation of a bidisperse pore structure of the adsorbent. Active and stable heterogeneous biocatalysts were prepared by the adsorptive immobilization of enzymatically active substances (glucoamylase and nongrowing baker’s yeast cells) on CFC.     

Effect of non-ionic surface active agents on TEOS-derived sols,gels and materials

The sol-gel process, starting from tetraethylorthosilicate precursor, is a suitable technique for the preparation of silica thin films. The use of specific organic additives, like non ionic surface-active agents, drastically modifies the gelation process and allows the preparation of microporous materials with a high microporous volume. The effects of additives on the sol, gel and material characteristics have been investigated by several methods such as ²⁹Si NMR, QELS, SAXS (for sols and gels), and N₂ adsorption, FESEM (for fired materials). It appears that the interactions of surface active agents with TEOS derived species limit condensation reactions and particle growing. A brittle gel structure is generated which leads to highly porous microporous silica after the elimination of organic chains by thermal treatment at 450°C. The material porous texture (specific surface area, pore size distribution and porous volume) can be varied especially by varying the surface active agent chain length and quantity. This kind of sol-gel system is suitable to prepare microporous silica membranes candidate for gas separation or catalytic reactor applications.     

Combustion synthesis and characterization of porous perovskite catalysts

Porous perovskite-type complex oxides LaCoO₃ and La_0·95Sr_0·05Ni_0·05Co_0·95O₃ were produced by combustion method. The properties of these porous materials such as crystal structures, particle sizes, surface patterns, pore size, surface area and pore volume were characterized by X-ray diffraction( XRD), scanning electron microscopy(SEM) and BET measurements. The results indicated that all porous materials are of the perovskite-type complex oxides. Doping Sr²⁺ ions on site A and doping Ni²⁺ ions on site B entered the crystal lattices of LaCoO₃ in the place of La³⁺ and Co³⁺, respectively, and the maximum peak of XRD patterns of doping sample was weaken and broaden. Morphological microscopy demonstrated agglomerates involved mostly thin smooth flakes and layers perforated by a large number of pores and its lamella decreased with the introduction of Sr²⁺ and Ni²⁺. Hysteresis loop in the N₂ adsorption-desorption isotherm of samples indicated its porous structures and the doping effect on its pore size, surface area and pore volume were improved. The porous catalysts have been tested for methane catalytic combustion and the results showed that these catalysts possessed high catalytic activity.     

Template-free sol–gel synthesis of microporous NiO–SiO2 composite with high surface area and narrow pore size distribution

Microporous NiO–SiO₂ composites were synthesized by a new sol–gel chemistry strategy using propylene oxide as gelation agent. Simple procedure, using of cheap precursor and high quality of the synthesized target materials were recognized as the advantages of the process. The obtained maximum pore surface area of the composites is about 718 m² g^?1 with narrow pore size distribution around 9 Å and micropore volume of 0.31 cm³ g^?1. It was found that the surface area of the samples decreases with the increase of Ni/Si molar ratio. However, the micropore size distributions of the samples were not altered with the increase of Ni/Si molar ratio. The unique chemistry of this sol–gel route assures the effectivity, simplicity and low cost of the whole process, showing the characteristics for the potential large scale preparation of microporous mixed oxide composites with very high pore area and very narrow pore size distribution.