影响热还原氧化石墨烯超级电容器性能的因素比较

通过改进的Hummer法制得氧化石墨烯,并在不同温度的氩气气氛中还原得到一系列热还原氧化石墨烯（T-RGO）. 电化学测试表明,T-RGO作为超级电容器电极材料时,良好的导电性是必需的,但石墨烯表面含氧官能团对其电容性能的影响要远大于导电性和比表面积的影响,900 °C还原的T-RGO比表面积为314 m²·g^-1电导率为2421 S·m^-1,但其容量只有56 F·g^-1,然而300 °C还原的T-RGO比表面积为18.8 m²·g^-1电导率为574 S·m^-1,其容量却达到281 F·g^-1. 材料表征分析表明,300 °C 还原的石墨烯之所以有更高的电容,是因为除双电层电容外,更多的是由其表面含氧官能团提供的赝电容,这使作者以后在设计制备超级电容器等储能设备用石墨烯基电极材料时更加有针对性.     

基于过渡金属硫化物/还原氧化石墨烯复合物的高性能超级电容器

组装高能量密度的非对称超级电容器需要使用比电容大、 体积变化小且循环稳定性好的电极材料. 过渡金属硫化物(TMSs)与纳米碳材料的复合物是此类电极材料之一. 采用水热法合成了由Cu-Mo硫化物在微波剥离的还原氧化石墨烯表面生长的复合材料(CuS-MoS₂/MErGO). 此复合材料在电流密度为2 A/g时具有高达861.5 F/g的比电容和良好的循环稳定性. 将1.6 V的电池电压施加在由NiS/MErGO为正极, CuS-MoS₂/MErGO为负极组装成的不对称超级电容器上时, 该电容器的功率密度为1.28 kW/kg, 且能量密度保持为54.2 W·h·kg^-1. 结果表明, TMS复合材料是一种很有前途的高性能电化学储能材料, 尤其是用于非对称超级电容器的组装.     

α-Fe2O3/石墨烯水凝胶复合材料的自组装制备及电化学性能

采用水热法自组装合成超薄α-Fe₂O₃/还原氧化石墨烯水凝胶（3DGH）复合材料.复合材料的物性表征和电化学测试结果表明,α-Fe₂O₃/3DGH材料呈三维多孔结构,直径约100 nm的α-Fe₂O₃颗粒均匀生长在还原氧化石墨烯片层上;通过调节复合材料中Fe³⁺的负载量,可实现α-Fe₂O₃颗粒的可控生长,粒径为200~30 nm;作为超级电容器的电极材料,α-Fe₂O₃粒径为100 nm左右时,铁负载量为40%的α-Fe₂O₃/3DGH复合材料具有最大的比电容（750.8 F/g,1 A/g）和循环稳定性（在10 A/g电流密度下,充放电5000次后比电容保持率为81.9%）,高于纯α-Fe₂O₃材料的比电容（251.6 F/g,1 A/g）和循环稳定性（充放电5000次后比电容保持率为43.8%）.     

三维还原氧化石墨烯/聚苯胺复合材料的制备及其超级电容性能

以制备的氧化石墨凝胶和聚苯胺纳米线为原料, 将二者按一定的质量比进行混合超声分散, 再以混合分散液为前驱体采用一步水热法制备得到三维还原氧化石墨烯(RGO)/聚苯胺(PANI) (RGP)复合材料, 采用扫描电镜(SEM), 透射电镜(TEM), X射线衍射(XRD), 傅里叶变换红外(FT-IR)光谱, X射线光电子能谱(XPS)和电化学测试等分析研究了复合材料的形貌、结构和超级电容性能. 结果表明, 复合材料既保持了还原氧化石墨烯的基本形貌, 又能使聚苯胺较好地镶嵌在还原氧化石墨烯的网状结构中; 且当氧化石墨与聚苯胺的质量比为1:1时复合材料在0.5 A·g^-1电流密度下比电容可高达758 F·g^-1, 即使在大电流密度(30 A·g^-1)下其比容量仍高达400 F·g^-1,在1A·g^-1电流密度下循环1000次后比容量保持率为86%, 表现出了良好的倍率性能和循环稳定性, 其超级电容性能远优于单纯的还原氧化石墨烯和聚苯胺, 其优异的超级电容性能可归咎于二者的相互协同作用.     

氢氧化镍纳米线/三维石墨烯复合材料的制备及其电化学性能

采用水热法制备了氢氧化镍纳米线/三维石墨烯复合材料及作为比较的三维石墨烯、氢氧化镍纳米线、还原氧化石墨烯和氢氧化镍纳米线/还原氧化石墨烯, 通过X射线衍射、扫描电镜、热失重分析和氮气吸脱附表征了材料的形貌、结构和组成, 并采用循环伏安法和恒电流充放电测试了复合材料的电化学性能. 结果表明: 氢氧化镍纳米线/三维石墨烯复合材料中直径为20-30 nm的氢氧化镍纳米线和三维结构的石墨烯紧密结合, 相互交联形成网状结构, 其比表面积达到136 m²·g^-1, 孔径分布20-50 nm, 氢氧化镍纳米线的含量达到88% (w,质量分数). 在6 mol·L^-1的KOH电解液中, 复合材料的比电容在1 A·g^-1电流密度下达到1664 F·g^-1, 在1 A·g^-1电流密度下循环3000 次后的比电容保持率为93%. 将复合材料的比电容和循环性能与氢氧化镍纳米线、氢氧化镍纳米线/还原氧化石墨烯、三维石墨烯和还原氧化石墨烯的性能进行比较, 发现三维石墨烯较还原氧化石墨烯具有更高的比表面积和三维多孔结构, 可以更大地提高活性物质的利用率, 进而提高复合材料的比电容和稳定性.     

硫化镍/三维网络石墨烯复合材料制备及其在高性能超级电容器的应用研究

本文在泡沫镍上生长三维网络状结构的石墨烯（3DG）,以此为模板合成石墨烯复合电极并将其应用于超级电容器. 采用一步水热法在3DG上合成得到Ni₃S₂纳米棒结构（Ni₃S₂/3DG）. 通过TEM、XRD、SEM和拉曼光谱等手段表征对Ni₃S₂/3DG复合材料的形态与结构进行表征. 电化学测试表明,Ni₃S₂/3DG复合材料具有高的比电容（在扫速为5 mV·s^-1下,具有1825.3 F·g^-1的比容量）和放电电容（在电流密度10 mA下电容高达516.7 F·g^-1）. 此外,在电流密度20 mA下具有良好的循环性能（循环1000周后仍能保留约100%的初始电容）. 本工作为得到高能量密度和良好的长期稳定性的复合材料提供了参考.     

具有高效电化学储能的中空网状笼还原氧化石墨烯

通过ZnO模板辅助电沉积法制备了中空网状笼还原氧化石墨烯,具有纳米管、多孔结构、网状结构和3D微米中空笼等多层次架构. 这样的结构能够同时促进电化学活性物种的传输,提高电极材料的利用率,以及提升超级电容器性能. 该类中空网状笼还原氧化石墨烯做超级充电器电极材料时表现出了优良的电化学性能,研究结果显示,在1.0 A•g^-1时比电容达到393 F•g^-1. 而且当电流密度从1.0 A•g^-1增加到20 A•g^-1,电容仅衰减了21.2%,10000周循环后比电容损失小于1%,表明具有优异的电容稳定性.     

纳米纤维素/还原氧化石墨烯复合材料用于高性能超级电容器

以高浓度氧化石墨烯(GO)溶液作为反应前驱体,纳米纤维素(NC)作为物理间隔物和电解液储存器,通过简单的一步水热法制备了纳米纤维素/还原氧化石墨烯(NC/rGO)复合材料,并探究了其作为超级电容器电极材料的潜力。结果如下：NC添加量为1 mL所制备的NC/rGO-1具有最佳电化学性能。基于NC/rGO-1的无黏合剂对称型超级电容器在0.3 A·g^-1的电流密度下显示出了269.33 F·g^-1和350.13 F·cm^-3的高质量和体积比电容,并在10.0 A·g^-1时仍能达到215.88 F·g^-1和280.62 F·cm^-3(其初始值的80.15%)。组装器件还显示出了较高的质量和体积能量密度(9.3 Wh·kg^-1和12.13 Wh·L^-1)和出色的循环性能(10 A·g^-1下10 000次循环后其初始比电容仅减少6.02%)。     

Mn3O4/石墨烯复合材料的制备与电化学性能研究

本文以氧化石墨烯（GO）溶液为氧化剂,采用水热法使GO直接氧化Mn(Ac)₂制备Mn₃O₄/石墨烯复合材料,并通过在制备过程中加入氨水提高了复合材料中GO的还原程度与Mn₃O₄颗粒的分散性. 制得的Mn₃O₄/石墨烯复合材料表现出优异的电化学性能. 在0.5 A·g^-1的电流密度下复合材料质量比容量可达到850 mAh·g^-1,0.5 A·g^-1时充放电循环测试200周容量保持率为99%.     

水热法制备Fe3O4/rGO纳米复合物作为锂离子电池阳极材料

以氢氧化铁为四氧化三铁的前驱体,氧化石墨烯（GO）为还原石墨烯（rGO）的前驱体,以水合肼和二水合柠檬酸三钠为混合还原剂,采用水热法制备了还原石墨烯负载四氧化三铁纳米颗粒（Fe₃O₄/rGO）的复合材料。通过透射电子显微镜（TEM）、X-射线衍射（XRD）和热重分析（TGA）对产物的形貌、结构和组成进行了表征。以锂片为对电极进行了扣式电池的组装,通过恒电流充放电和循环伏安法对其电化学性能进行了测试。材料具有均一的形貌,rGO具有较高的还原程度且可以在充放电过程中缓冲Fe₃O₄纳米颗粒的体积变化,使得Fe₃O₄/rGO纳米复合物具有较好的电化学性能。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.