高活性、可循环的Pt-Cu@3D石墨烯复合催化剂的制备和催化性能（英文）

以氧化石墨烯为前驱体,通过氧化还原法制备了具有三维大孔稳定结构的Pt-Cu@3D石墨烯催化剂。作为载体,三维石墨烯的宏观大孔结构具有大比表面积,可以更好地促进催化反应中的传质过程。以对硝基苯酚的还原为模型反应,通过实验确定Pt与Cu的最佳质量比为3:5,利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、X射线衍射(XRD)和能量色散X射线光谱(EDX)等方法对最优催化剂的结构进行了表征。催化测试表明复合催化剂在对硝基苯酚还原反应中具有高效稳定、低成本、可循环的良好性能。     

三维(3D)石墨烯及其复合材料的应用

三维（3D）石墨烯通常是指具有3D结构的二维（2D）石墨烯组装体,是近年来石墨烯化学领域的新型功能性材料。将2D石墨烯片整合成具有3D结构的组装体可以有效调控石墨烯的电学、光学、机械、化学和催化特性,因此3D石墨烯材料不仅具有石墨烯固有的理化性质,其三维多孔的微/纳米结构还使其兼具比表面积大、机械强度高、电子传导能力优越及传质快速等优良特性。这些独特的性质使3D石墨烯及其复合材料在材料科学领域备受关注。研究发现,3D石墨烯及其复合材料应用于纳米电子学、能量储存和转换、化学和生物传感等研究领域均表现出优越的性能。本文结合当前研究热点,综述了3D石墨烯及其复合材料在催化、储氢/气体吸附、传感器、环境修复、超级电容器等领域中的应用进展,并简要评述目前3D石墨烯材料应用中所面临的挑战及发展前景。     

石墨烯负载Pt催化剂的催化氧化发光性能

利用溶胶固定化工艺合成了石墨烯负载Pt纳米颗粒的Pt/石墨烯催化剂.研究了分散在石墨烯上的Pt颗粒尺寸和负载量对CO催化发光性能的影响规律,探查了催化剂的某些分析特性及对其它气相体系的催化氧化性能.结果表明,Pt纳米颗粒可以很好地分散在石墨烯表面,并有较快的催化反应速率,Pt颗粒越小催化发光强度越大.当不同Pt负载量(0.4%-1.6%(w,质量分数))的催化剂作用于40%(φ,体积分数)以下浓度的CO/空气体系时,产生的催化发光强度均与CO浓度成正比,其中以负载量0.8%最优;但随CO浓度继续增加,低Pt负载量(0.4%,0.8%)催化剂的发光强度下降,而高Pt负载量(1.2%,1.6%)催化剂的发光强度继续上升,且Pt负载量越高,催化氧化发光能力越强.该催化剂在一定条件下,不但对CO氧化有较好的催化发光性能,还对乙醚、无水甲醇和甲苯有不同程度的催化氧化发光活性;但二氧化碳、甲醛、戊二醛、丙酮、乙酸乙酯、三氯甲烷、水蒸气均无响应信号.     

石墨烯负载Pt/Co双金属纳米颗粒催化剂的制备及催化制氢性能

采用化学共还原方法制备了石墨烯负载Pt/Co双金属纳米颗粒（GBNPS）催化剂,并将其用于催化硼氢化钾（KBH₄）水解制氢.采用透射电子显微镜（TEM）、X射线衍射（XRD）仪和X射线光电子能谱（XPS）表征了该催化剂,并研究了双金属纳米颗粒的化学组成对其催化KBH₄水解制氢性能的影响.结果表明,制备的石墨烯负载Pt/Co双金属纳米颗粒平均粒径为3.2~3.9 nm,其中石墨烯负载Pt₂₀Co₈₀双金属纳米颗粒的催化活性最高,35℃时制氢活性可达35973 mol_H2·h^-1·mol^-1_Pt,且具有良好的耐久性,催化KBH₄水解反应的表观活化能为36 kJ/mol.     

中空铂镍/三维石墨烯催化剂的制备及电化学性能

采用超声辅助化学法和凝胶化反应相结合的工艺制备了中空铂镍/三维石墨烯电催化剂(PtNi/GCM). 利用X射线粉末衍射仪(XRD)、 X射线光电子能谱仪(XPS)、 扫描电子显微镜(SEM)和透射电子显微镜(TEM)等表征了催化剂的结构、 组成及微观形貌. 采用电化学工作站和旋转圆盘电极测试了催化剂对氧还原反应的电催化活性和稳定性. 结果表明, 铂和镍前驱体的不同摩尔比对催化剂的多孔结构、 粒子形貌和分散状态影响较大, 当摩尔比为1∶1时, 所得三维石墨烯中纳米粒子尺寸均一、 分散均匀. 该PtNi/GCM催化剂对氧还原具有优异的催化活性, 在半波电势(0.494 V)处, 质量比活性和面积比活性分别为1.09 A/mgPt和1.02 mA/cm², 是商业Pt/C的5.4倍和3.5倍(0.20 A/mg_Pt, 0.29 mA/cm²). 同时, 该催化剂还具有很好的稳定性, 循环30000周后, 半波电势降低值是商业铂炭的43.6%.     

铜/石墨烯复合材料的制备及催化性能

采用水热法制备铜/石墨烯(Cu/RGO)复合材料,通过XRD、FTIR、SEM和TEM对材料的结构和形貌进行表征,并考察了复合材料在H₂O₂辅助作用下对次甲基蓝(MB)的催化作用。结果表明,该复合材料中石墨烯所负载的铜颗粒尺寸较小且分布均一,对MB的催化效果良好,0.18 g·L^-1复合催化剂在300 min内对MB的脱色效果可达90.7%,经过5次循环仍有88.0%以上。     

铜/石墨烯复合材料的制备及催化性能

采用水热法制备铜/石墨烯(Cu/RGO)复合材料,通过XRD、FTIR、SEM和TEM对材料的结构和形貌进行表征,并考察了复合材料在H_2O_2辅助作用下对次甲基蓝(MB)的催化作用。结果表明,该复合材料中石墨烯所负载的铜颗粒尺寸较小且分布均一,对MB的催化效果良好,0.18 g·L~(-1)复合催化剂在300 min内对MB的脱色效果可达90.7%,经过5次循环仍有88.0%以上。     

WO_3纳米棒/石墨烯复合材料的制备及电化学储锂性能

以氯化钨和氧化石墨烯(GO)为原料,乙醇为溶剂,一步合成了WO3纳米棒/石墨烯纳米复合材料(WO3/RGO).将WO3/RGO纳米复合材料用于锂离子电池负极,并通过充放电测试、循环伏安(CV)和电化学阻抗谱(EIS)技术综合考察了该材料的储锂性能.结果显示,在0.1C(1C=638 mA?g-1)倍率下,复合物的首次放电比容量达到761.4 mAh?g-1,100次循环后可逆容量仍保持在635 mAh?g-1,保持率为83.4%.即使在5C倍率下容量仍高达460 mAh?g-1.由此说明,WO3/RGO纳米复合物具有优异的循环稳定性及倍率性能,可望用于高性能锂离子电池.     

具有三维导电网络结构的锡纳米颗粒/石墨烯纳米片复合电极材料的储镁性能研究

镁二次电池具有安全性高、价格低廉等优点,是一种具有潜在应用前景的高能量密度电池体系.目前,镁二次电池的研究重点之一是寻找合适的电极材料.最近,我们通过水热和热处理相结合的方法成功制备了具有三维导电网络结构的锡纳米颗粒/石墨烯纳米片复合电极材料.研究发现,在石墨烯的三维导电网络片层上,均匀分布了粒径小于100 nm的锡纳米颗粒.将锡纳米颗粒/石墨烯纳米片复合材料作为镁二次电池电极材料,当电流密度为15 mA·g^-1和300 mA·g^-1时,首次放电容量分别达到了545.4 mAh·g^-1和238.8 mAh·g^-1,经过150圈后,容量保持率达到了93%,库伦效率为99%,表现出了较高的电化学活性.研究还发现,镁离子嵌入复合材料中形成镁锡合金,当镁离子脱出后,再次形成锡纳米颗粒/石墨烯纳米片复合电极材料,镁离子的脱出和嵌入具有很高的可逆性.这对未来研究设计高性能镁离子电极材料具有十分重要的意义.     

银耳状Fe-N-C复合催化剂的制备及催化氧还原性能研究

以无机铁盐和邻苯二胺为基础原料,经铁基螯合前驱体热解反应,制备出Fe-N-C复合催化剂.经扫描电镜观察,带有折褶的碳微纳米片相互交迭,形成银耳状的三维自支撑结构.氮气吸脱附测试表明此结构富含微孔和介孔,比表面积可达290 m2/g.通过X射线衍射(XRD)确证石墨化C和多晶Fe3C作为催化剂主相存在, X射线光电子能谱(XPS)进一步揭示N原子主要以石墨N和吡啶N形式掺杂到C骨架中.电化学测试表明银耳状Fe-N-C复合催化剂在碱性条件下催化氧还原反应为四电子过程,其催化活性可媲美商业Pt/C催化剂.经过2000次氧还原测试后,催化极限电流衰减小于5%,并且半波电势仅负移5 mV(商业Pt/C催化剂负移35 mV),表现出优异的氧还原催化稳定性.     

Chiral Chromium Salen@rGO as Multipurpose and Recyclable Heterogeneous Catalyst

The first immobilization of a pyrene-tagged chromium salen complex through π-π noncovalent interactions on reduced graphene oxide (rGO) is described. A very robust supported catalytic system is obtained to promote asymmetric catalysis in repeated cycles, without loss of activity or enantioselectivity. This specific behavior was demonstrated in two different catalytic reactions (up to ten reuses) promoted by chromium salen complexes, the cyclohexene oxide ring-opening reaction and the hetero-Diels-Alder cycloaddition between various aldehydes and Danishefsky's diene. Furthermore, the chiral chromium salen@rGO has been found to be compatible with a multi-substrate type use, in which the structure of the substrate involved is modified each time the catalyst is reused.     

MgO Nanoparticles as a Recyclable Heterogeneous Catalyst for the Synthesis of Polyhydroquinoline Derivatives under Solvent Free Conditions

Magnesium oxide nanopartticels in average size between 35–120 nm were prepared by sonochemistry method. Synthesis of polyhydroquinoline derivatives using MgO nanoparticles from the reaction of dimedone, benzaldehyde, ethyl acetoacetate and ammonium acetate under solvent‐free conditions is reported. Easy handling, reusability, thermal stability and non‐toxicity of the catalyst make the present protocol as an eco‐friendly and economically acceptable method for synthesis of these heterocycles.     

Gold and Silver Nanoparticles Supported on Metal-organic Frameworks: a Highly Active Catalyst for Three-component Coupling Reaction

Engineering metal-organic frameworks(MOF) for heterogeneous catalysts have been of extreme interest since they have large pore size within the crystalline framework and well defined pore architecture. Ni-containing MOF Ni₂(3,5-Pydc)₂(H₂O)₈·2H₂O(1·H₂O) was prepared by solvothermal method from 3,5-pyridinedicarboxylic acid, D-camphoric acid and Ni(NO₃)₂·6H₂O in dimethylformamide(DMF)/water(volume ratio 2:1). And two gold and silver functionalized 1·H₂O catalysts were prepared by impregnation method. Catalysts 2.53%Au/MOF and 4.23%Ag/MOF were in-depth characterized by single crystal X-ray diffraction, powder X-ray diffraction(PXRD), thermogravimetric analysis(TGA), transmission electron microscopy(TEM), and inductively coupled plasma-atomic emission spectroscopy(ICP-AES). Their catalytic performance was examined in one-pot synthesis of structurally divergent propargylamines via three component coupling of aldehyde, alkyne, and amine(A³) in 1,4-dioxane. The results show that the catalysts all displayed high reactivities, and a selectivity of 100% for propargylamines. Catalysts 2.53%Au/MOF and 4.23%Ag/MOF have proved to be applicable to a wide range of substrates. Catalysts 2.53%Au/MOF and 4.23%Ag/MOF can be easily recycled and used repetitively at least 3 times with a slight drop in activity. These features render the catalysts particularly attractive in the practice of propargylamines synthesis in an environmentally friendly manner.     

Cu(PPh3)2BH4作还原剂制备PtCu/C催化剂催化烯烃硅氢 加成反应研究

采用湿法浸渍, Cu(PPh3)2BH4作为还原剂制备了负载型PtCu/C双金属催化剂, Pt∶Cu原子比为0.5～2.0. 用于苯乙烯与三乙氧基硅烷加成反应, Cu元素的引入使Pt/C催化剂的催化性能得到提高, 表现出比Speier催化剂、Karestedt催化剂和Pt/C催化剂更好的β-加成产物选择性. 催化直链烯烃与三乙氧基硅烷加成反应表现出优良的催化性能, 并且催化剂可重复使用.     

石墨炔孔结构:设计、合成和应用

石墨炔作为一种新兴碳材料, 由于具有特殊的电子特性、 丰富的纳米级孔隙以及能在相对低温下合成的特点, 在催化、 能源及生物等领域受到广泛关注. 石墨炔自下而上的合成特点使其在结构上具有可设计性, 而其显著特征在于具有拓扑有序的规则孔道结构. 在过去的10年间, 研究人员在石墨炔孔结构设计方面进行了大量的实验和理论研究. 孔结构设计所带来的独特性能为其提供了良好的应用前景. 本文从石墨炔的合成特点出发, 总结了单体、 催化剂、 模板及溶液4个因素对石墨炔结构的影响, 并从孔结构出发讨论了其应用. 为研究者以应用为导向, 设计合成具有特殊孔结构的石墨炔提供了思路. 最后还探讨了孔结构设计给石墨炔带来的机遇与挑战, 并对三维多孔结构石墨炔的设计进行了展望.     

MOF-808 as a Highly Active Catalyst for the Diastereoselective Reduction of Substituted Cyclohexanones

Zr-containing MOF-808 is an excellent heterogeneous catalyst for the diastereoselective Meerwein–Ponndorf–Verley reduction of substituted cyclohexanones. The presence of substituents at the 2 or 3 position of the cyclohexanone ring strongly drives the reaction towards the formation of one of the two possible isomers. For 3-methyl cyclohexanone, the available space inside the MOF pores allows the formation of the bulkier transition state leading to the thermodynamically stable 3-cis-cyclohexanol. For 2-methyl cyclohexanone, the reaction rate is much slower and the final diastereoselectivity depends on the size of the alcohol used. Finally, reduction of 2-phenyl cyclohexanone is considerable faster over MOF-808 than for any other catalyst reported so far. The large size of the phenyl favors the selective formation (up to 94% selectivity) of the cis-alcohol, which goes through a less hindered transition state.     

Ultrafine Molybdenum Carbide Nanoparticles Composited with Carbon as a Highly Active Hydrogen‐Evolution Electrocatalyst

The replacement of platinum with non‐precious‐metal electrocatalysts with high efficiency and superior stability for the hydrogen‐evolution reaction (HER) remains a great challenge. Herein, we report the one‐step synthesis of uniform, ultrafine molybdenum carbide (Mo₂C) nanoparticles (NPs) within a carbon matrix from inexpensive starting materials (dicyanamide and ammonium molybdate). The optimized catalyst consisting of Mo₂C NPs with sizes lower than 3 nm encapsulated by ultrathin graphene shells (ca. 1–3 layers) showed superior HER activity in acidic media, with a very low onset potential of ?6 mV, a small Tafel slope of 41 mV dec^?1, and a large exchange current density of 0.179 mA cm^?2, as well as good stability during operation for 12 h. These excellent properties are similar to those of state‐of‐the‐art 20 % Pt/C and make the catalyst one of the most active acid‐stable electrocatalysts ever reported for HER.     

Chitosan-immobilized Palladium Complex：a Green and Highly Active Heterogeneous Catalyst for Heck Reaction

A green heterogeneous catalyst for Heck reaction-chitosan-immobilized palladium complex was prepared.The catalyst exhibits high activity and stereoselectivity under the moderate reaction conditions.The catalyst can be separated easily from the reaction mixture and reused after washing.Under the suitable reaction conditions,the cross-coupling of iodobenzene (ArI) with acrylic acid (AA) or acrylate can be achieved 93.3% or 99% yield of trans-cinnarnic acid or trans-cinnamic ester.