氮掺杂石墨烯的制备及氧还原电催化性能

采用两步热解法, 用尿素掺杂氧化石墨烯(GO)得到N掺杂的还原氧化石墨烯(N-RGO), 通过控制反应温度, 制备了具有不同电催化活性的N掺杂的还原氧化石墨烯. 透射电子显微镜(TEM)和扫描电子显微镜(SEM)结果显示, 制得的氮掺杂石墨烯(nG)表面褶皱和重叠增加. X射线光电子能谱(XPS)证明, 氮元素以吡啶N、 吡咯N和石墨化的N 3种形式掺杂在石墨烯中, 最高摩尔分数为6.6%. 通过循环伏安(CV)和旋转圆盘电极(RDE)测试了nG的电化学性能, 结果表明, 在酸性电解质中对氧还原(ORR)有较高的催化活性, 起始电位在0.1 V左右, 电催化还原氧气时主要为四电子反应, 且相对商用的Pt/C催化剂有更好的电化学稳定性, 其中第一步热解温度为200℃制得的nG催化性能最好.     

氮掺杂还原氧化石墨烯负载铂催化剂的制备及甲醇电氧化性能

采用高温热解聚苯胺修饰的氧化石墨烯（PANI-GO）,得到了氮掺杂的还原氧化石墨烯碳材料（N-RGO）,以其负载Pt 制备了Pt/N-RGO纳米结构电催化剂. 采用透射电镜（TEM）、X射线光电子能谱（XPS）、X 射线衍射（XRD）谱及拉曼光谱等技术对N-RGO和Pt/N-RGO的形貌及结构进行了表征,用循环伏安、计时电流等电化学技术研究了Pt/N-RGO电极催化剂对CO溶出反应和甲醇电氧化反应的催化性能. 结果表明：高温热解PANIGO可同时实现GO的还原及其氮掺杂的过程,氮掺杂引起还原氧化石墨烯碳材料表面缺陷结构和导电性的增加;与相应的未掺杂氮样品Pt/RGO相比较,Pt/N-RGO样品上Pt 颗粒的分散更均匀,显示出更强的抗CO毒化能力和更高的甲醇电氧化催化活性及稳定性.     

氮掺杂还原氧化石墨烯负载铂催化剂的制备及甲醇电氧化性能

采用高温热解聚苯胺修饰的氧化石墨烯(PANI-GO),得到了氮掺杂的还原氧化石墨烯碳材料(N-RGO),以其负载Pt制备了Pt/N-RGO纳米结构电催化剂.采用透射电镜(TEM)、X射线光电子能谱(XPS)、X射线衍射(XRD)谱及拉曼光谱等技术对N-RGO和Pt/N-RGO的形貌及结构进行了表征,用循环伏安、计时电流等电化学技术研究了Pt/N-RGO电极催化剂对CO溶出反应和甲醇电氧化反应的催化性能.结果表明:高温热解PANIGO可同时实现GO的还原及其氮掺杂的过程,氮掺杂引起还原氧化石墨烯碳材料表面缺陷结构和导电性的增加;与相应的未掺杂氮样品Pt/RGO相比较,Pt/N-RGO样品上Pt颗粒的分散更均匀,显示出更强的抗CO毒化能力和更高的甲醇电氧化催化活性及稳定性.     

氮掺杂还原氧化石墨烯/四氧化三钴双功能催化剂的制备及表征

采用尿素作为氮源,通过热退火法制备氮掺杂还原氧化石墨烯,然后以乙酰丙酮钴作为钴源通过水热法制备氮掺杂还原氧化石墨烯/四氧化三钴杂化纳米片作为催化氧还原和氧析出反应的双功能催化剂。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线电子能谱仪(XPS)等对其进行形貌结构表征,通过旋转圆盘电极等电化学测试对其电催化性能进行分析,可以看出该催化剂具有良好的氧还原和氧析出催化性能。     

甲基丙烯酸缩水甘油酯功能化石墨烯的制备与表征

利用改进的Hummers法对天然鳞片石墨进行氧化处理制备氧化石墨烯,将其与甲基丙烯酸缩水甘油酯(GMA)在温和条件下反应,再经水合肼还原得到功能化石墨烯.分散性测试结果表明,超声后的功能化石墨烯可以稳定分散于丙酮、乙醇和N,N-二甲基甲酰胺等有机溶剂中.采用傅里叶变换红外光谱、X射线衍射分析及X射线光电子能谱对样品的结构进行了表征.结果表明,GMA上的环氧基与氧化石墨烯上的羟基发生了化学反应,键合在氧化石墨烯表面;经水合肼还原后,层间距较功能化氧化石墨烯缩小,无序度增加.扫描电子显微镜(SEM)测试结果表明,功能化石墨烯含大量褶皱和卷曲;原子力显微镜(AFM)测试结果表明,功能化石墨烯的厚度为2~3 nm.热重分析结果表明,还原氧化石墨烯的热稳定性最高,功能化石墨烯次之,氧化石墨烯的热稳定性最低.     

高活性离子液体催化棉籽油酯交换制备生物柴油

 制备了五种对水稳定性好、带-SO3H 官能团的Bronsted酸离子液体,并用它们催化棉籽油酯交换反应制备生物柴油. 结果表明,磺酸类Bronsted酸离子液体具有很好的催化活性,其催化活性与阳离子中的含氮官能团和碳链长度有关,吡啶丁烷磺酸硫酸氢盐离子液体的催化活性最好,其活性接近于浓硫酸催化剂. 离子液体容易同产物分离,具有很好的稳定性,可以循环使用,对环境友好,是制备生物柴油的较理想催化剂.     

基于多金属氧酸盐的介孔离子催化剂催化苯一步氧化制苯酚（英文）

苯酚是一种重要的有机化工原料,工业上主要采用合成路线长、原子利用率低、能耗高、环境污染严重的异丙苯法生产.当前,随着绿色化学的普及,H_2O_2催化苯一步氧化制苯酚受到越来越多的关注.在研究的众多催化剂中,钒取代杂多酸被认为是该反应最有效的催化剂之一.然而,纯杂多酸易溶于H_2O_2催化的苯羟基化反应体系,导致污染严重、后处理和分离困难.为了获得可回收的固体杂多酸催化剂,通常将其负载于多孔载体上,但这种方法常伴随着活性组分易溶脱,反应速率慢等缺点.因此,在H_2O_2催化苯一步氧化制苯酚体系中获得高效、可重复使用的杂多酸基固体催化剂仍然是一个挑战.采用有机单元修饰杂多酸是制备杂多酸基固体催化剂的有效方法.研究表明,有机基团的引入可以有效调控杂多酸的溶解性和氧化还原性.另一方面,催化剂中的疏水微环境也能有效促进非极性底物与催化活性中心的相互作用,提高反应速率,改善催化活性.因此,我们通过离子交换法将对二甲苯型双核咪唑离子液体阳离子与含钒杂多阴离子结合,研究制备了一种具有疏水微环境的介孔杂多酸基离子固体催化剂.采用傅里叶变换红外光谱、X射线衍射、扫描电镜、N2吸附-脱附和CHN元素分析等表征手段对催化剂进行全面分析.结果表明,该催化剂是一种具有较高比表面积的半无定形疏水有机杂多酸盐.在H_2O_2催化的苯一步氧化制苯酚反应中引导了液-固两相催化体系,在反应时间1 h,反应温度70 oC,苯酚产率可达到28.9%,与均相纯杂多酸的催化活性基本相当,且催化剂重复使用性能良好.催化剂构效关系和反应动力学研究表明,高比表面积和疏水微环境的构建加快了苯与催化活性中心的相互作用,提高了催化反应速率和产物选择性.同时,咪唑基离子液体阳离子通过分子内的电子相互作用改善了杂多阴离子的氧化还原能力,也赋予固体催化剂更高的催化活性.该研究为H_2O_2催化苯一步氧化制苯酚反应提供了一种制备简单,经济高效,可重复使用的杂多酸基固体催化剂.     

氧化石墨烯负载席夫碱钯催化剂的合成、表征及对Suzuki反应催化性能的研究

以修饰的Hummers法制备的氧化石墨烯为载体,席夫碱为配体制备了一种新型的负载型钯催化剂,采用红外光谱仪、透射电镜、X射线光电子能谱仪、热重分析仪和X射线衍射仪等手段对负载型催化剂进行了表征,并评价了其对水相Suzuki反应的催化活性.结果表明,该催化剂在较温和的实验条件下即可高效催化水相芳基卤与芳基硼酸的Suzuki反应,催化剂重复使用5次后,活性基本不变.     

几种载体载Ni催化剂上苯直接羟基化制备苯酚的研究

本文利用浸渍法制备了一系列不同载体的镍基催化剂,并将其用于苯的羟基化反应.用等离子原子直读光谱、粉末X射线衍射分析、比表面测试等对所制备的催化剂进行了表征.发现在所制备的催化剂中,以γ-Al2O3为载体的Ni1.7/γ-Al2O3 催化剂在苯的羟基化反应中具有相对较好的催化活性和选择性,而在Ni/TiO2和Ni/NaX上,则苯酚的深度氧化严重.     

自由基反应诱导的溴功能化还原氧化石墨烯的制备

以氧化石墨烯(GO)为原料,N-溴代丁二酰亚胺(NBS)为溴代试剂,硫代硫酸钠为还原剂,通过羧基化、溴化和还原三步法,采用自由基反应的方式制备了溴功能化还原氧化石墨烯(rGOBr).通过X射线衍射、扫描电子显微镜、红外光谱、拉曼光谱以及X射线光电子能谱等手段对rGOBr的结构、微观形貌和元素组成进行了表征.结果表明,溴元素以共价键的形式分布在石墨烯表面.本方法原料来源广泛、操作简单且条件温和,为石墨烯的溴功能化提供了一条新途径.     

Utilisation of Non-Edible Source (Pongamia pinnata Seeds Shells) for Producing Methyl Esters as Cleaner Fuel in the Presence of a Novel Heterogeneous Catalyst Synthesized from Waste Eggshells

Waste eggshells were considered for synthesising a precursor (CaO) for a heterogeneous catalyst, further impregnated by alkali caesium oxide (Cs₂O). The following techniques were used to characterise the synthesised catalysts: X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and Temperature Programmed Desorption (CO₂-TPD). The synthesised catalyst revealed its suitability for transesterification to produce biodiesel. The biodiesel production process was optimised, and it showed that the optimal biodiesel yield is 93.59%. The optimal set of process parameters is process temperature 80 °C, process time 90 min, methanol-to-oil molar ratio 8 and catalyst loading 3 wt.%. It has been found that the high basicity of the catalyst tends to give a high biodiesel yield at low methanol-to-oil ratio 8 when the reaction time is also less (90 min). The fuel properties of biodiesel also satisfied the standard limits defined by ASTM and the EN standards. Thus, the synthesised catalyst from waste eggshells is highly active, improved the biodiesel production conditions and PPSS oil is a potential nonedible source.     

纯四方相硫化氧化锆催化剂的制备及其生物柴油合成应用研究

将过硫酸铵浸渍于直接合成的纳米氧化锆晶体表面,经300-500℃高温焙烧处理获得硫化氧化锆催化剂。采用X射线衍射（XRD）、氮气吸附-脱附、氨气程序升温脱附（NH₃-TPD）、傅里叶红外光谱（FT-IR）、扫描电镜（SEM）和能谱仪（EDS）等分析手段对催化剂的结构性能进行了表征。结果表明,所有的催化剂均展现出纯四方相结构和高的结晶度。其中,经500℃热处理获得的催化剂拥有最高的硫含量和酸性位,将其应用于大豆油与甲醇酯交换反应合成生物柴油,获得了脂肪酸甲酯收率高达84.6%的催化效果,进一步表明该催化剂表面存在优越的超强酸位。     

Turkish perlite supported nickel oxide as the heterogeneous acid catalyst for a series of Claisen–Schmidt condensation reactions

Potentially active and eco-friendly solid acid catalysts have been synthesized by loading different weight percentages (10, 15, and 50) of nickel oxide on thermally activated Turkish perlite through the deposition-precipitation method. Structural features of prepared catalysts were analyzed using BET surface area analysis, X-ray diffraction, scanning electron microscope (SEM), SEM-EDX, transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR), pyridine adsorbed FT-IR, UV-Vis diffuse reflectance spectroscopy (DRS), and thermogravimetric analysis (TGA) techniques. Pyridine adsorbed FT-IR analysis confirmed the presence of the optimum amount of Bronsted acidic sites in a catalyst having 15 wt. % loading of nickel oxide, which was tested for catalyzing a series of Claisen–Schmidt condensation of cyclohexanone and aromatic aldehydes to produce good isolated yield (90%–93%) of 2,6-bis(substituted benzylidene)cyclohexanones, significantly used in anti-tumor and cytotoxic activities. The high catalytic efficiency of the chosen catalyst remains almost intact up to six reaction cycles. On higher wt. % loading of nickel oxide, crystallite size increases along with agglomeration of larger nickel oxide particles on catalyst surface resulting in pore blockage and poor catalytic activity. Loading of NiO on the surface of thermally activated Turkish perlite was confirmed by SEM-EDX analysis, and TEM observations show that the particle size of the preferred catalyst was less than 50 nm. Based on results drawn from XRD, FT-IR, pyridine adsorbed FT-IR, UV-Vis DRS studies, model structures were proposed for Turkish perlite and all prepared catalysts. During this work, the catalytic potential of the preferred catalyst was compared with other previously reported catalysts, and it showed appreciable results. The formed products were further confirmed by their melting point and ¹H-NMR analysis.     

Electrochemistry at chemically modified graphenes

Electrochemical applications of graphene are of great interest to many researchers as they can potentially lead to crucial technological advancements in fabrication of electrochemical devices for energy production and storage, and highly sensitive sensors. There are many routes towards fabrication of bulk quantities of chemically modified graphenes (CMG) for applications such as electrode materials. Each of them yields different graphene materials with different functionalities and structural defects. Here, we compare the electrochemical properties of five different chemically modified graphenes: graphite oxide, graphene oxide, thermally reduced graphene oxide, chemically reduced graphene oxide, and electrochemically reduced graphene oxide. We characterized these materials using transmission electron microscopy, Raman spectroscopy, high-resolution X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry, which allowed us to correlate the electrochemical properties with the structural and chemical features of the CMGs. We found that thermally reduced graphene oxide offers the most favorable electrochemical performance among the different materials studied. Our findings have a profound impact for the applications of chemically modified graphenes in electrochemical devices.     

Amberlyst-15型离子交换树脂催化γ-丁内酯酯交换反应的研究

从反应温度、时间、催化剂的用量、催化剂的重复使用、产物的分离等方面系统研究了γ-丁内酯与甲醇的酯交换反应,得到了优化的反应条件,即,反应温度为28℃,反应时间为10h,γ-丁内酯/甲醇/Amberlyst-15为0.9∶12.5∶12.5(V/V/m)。在该反应条件下,酯交换产物的分离产率达到77%。同时考察了γ-丁内酯与其它6种醇的酯交换反应,证明了在较高反应温度下,该树脂对其它醇仍有较好的催化活性(产物的质量百分数为50%～60%)。然而,随着醇体积的增大,反应的转化率逐渐下降。     

Thermogravimetry study of the ester interchange of sunflower oil using Mg/Al layered double hydroxides (LDH) impregnated with potassium

Mg/Al layered double hydroxides (LDH) containing KI were synthesized and tested as basic heterogeneous catalysts for transesterification of sunflower oil, in order to obtain biodiesel. The process was carried out using reflux with 15:1 molar ratio of methanol to sunflower oil, and catalyst concentration of 2 mass%. The characterization of sunflower oil and biodiesel was accomplished according to ASTM and EN standard methods. The gas chromatographic and TG/DTG profiles were evaluated, and the results of yield and conversions were compared. The gas chromatographic analysis showed that the catalysts were effective in converting vegetable oil into biodiesel, specially using LDH catalysts modified with KI and molar ratio Mg/Al = 1, with conversions higher than 99 % indicating the strong influence of the chemical composition and controlled basicity, due to the presence of potassium in the structure of the catalyst.     

Solvothermal reduction of graphene oxide in dimethylformamide

The reduction of graphene oxide (G-O) is one of the most promising methods for the large scale production of graphene-based materials. In this paper, we report a simple and non-toxic method to produce reduced graphene oxide (rG-O) by refluxing G-O in N, N-dimethylformamide without the aid of a reducing agent. The rG-O materials with high degrees of reduction are prepared and the levels of reduction are controlled using reflux time. Successful reduction is confirmed by combustion-based elemental analysis and X-ray photoelectron and Fourier transform infrared spectroscopy.     

Preparation of chloro-functionalized reduced graphene oxide by silver-catalyzed radical reaction

It is well-known that chemical functionalization of graphene has the great significance.We report the development of a new synthesis method of chloro-functionalized reduced graphene oxide(rGOCl).The rGOCl was prepared by radical reaction,and treatment of carboxyl graphene oxide(GOCOOH) with N-chlorosuccinimide(NCS) at 90℃ for 10 h under an atmosphere of nitrogen,using silver nitrate as catalyst.The morphologies and structures of the prepared materials were investigated by field-emission scanning electron microscopy(FESEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),Raman spectroscopy and the thermal gravimetric.Results indicated that the rGOCl can be readily obtained from graphene oxide(GO) in three steps.     

氮掺杂石墨烯的生长机理及其在乙苯选择性氧化中的应用

以热解氧化石墨烯材料为碳基底,分别使用有机氮源和无机氮源对其进行氮掺杂处理,制备了一系列氮掺杂石墨烯材料.采用透射电子显微镜、扫描电子显微镜、拉曼光谱和X射线光电子能谱等表征方法考察了氮掺杂石墨烯的生长机理.结果表明,随着制备过程中退火温度的改变,氮掺杂石墨烯中不同氮物种的含量有显著差别.这种差异是由不同氮物种化学环境的差异所导致的.所制备的含氮石墨烯材料对乙苯选择性氧化制苯乙酮反应均表现出优良的催化活性.其中,石墨氮的含量对于提高苯乙酮收率起到至关重要的作用.此外,通过氧化剂控制活化的方法可以消除过多的结构缺陷和过量氮掺杂对催化反应的不利影响,有效提升氮掺杂石墨烯的催化活性.     

Eco-friendly synthesis, characterization and properties of a sodium carboxymethyl cellulose/graphene oxide nanocomposite film

A previously unreported nanocomposite (CMC/GO) high-performance film was prepared by a simple solution mixing-evaporation method. The structure, thermal stability, and mechanical properties of the composite films were investigated by wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, thermogravimetry analysis, and mechanical testing. The results obtained from these different studies revealed that CMC and graphene oxide were able to form a homogeneous mixture. Compared with pure CMC, the tensile strength and Young’s modulus of the graphene-based materials were improved significantly upon incorporation of 1 wt% graphene oxide by 67 ± 6 % and 148 ± 5 %, respectively. In addition, the DMA composite films also showed a high storage modulus up to 250 °C.