微波固相法快速制备氮掺杂石墨烯

以鳞片石墨为原料,首先通过Hummers法制备氧化石墨,再将洗涤至中性的氧化石墨分散液与乙二胺反应得到功能化石墨烯。干燥后的功能化石墨烯在微波辐照下能瞬间产生高热,促使接枝的乙二胺分子分解并实现对石墨烯原位掺杂制备出氮掺杂石墨烯。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)、X射线衍射(XRD)、X射线能谱(EDS)对样品的形貌、结构和组成进行了表征。结果表明:该合成途径能成功实现对氧化石墨烯的还原和掺杂,所合成的氮掺杂石墨烯呈现透明绢丝状结构。     

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.     

微波溶剂热法制备掺氮石墨烯用于碱性氧还原反应

采用微波处理氧化石墨烯(GO)与乙二醇(EG)、乙二胺(ED)混合液的方法制备氮掺杂石墨烯(NG),使用旋转圆盘电极对NG催化氧还原在碱性溶液中反应进行研究,并考察了不同微波辐射时间、ED与EG之比对反应性能的影响。采用X射线衍射仪(XRD)、透射电子显微镜(TEM)、拉曼光谱(Raman)和傅里叶变换红外光谱(FT-IR)研究了NG催化剂的结构与性质。相比于未掺氮的石墨烯样品,NG表现出更正的起始电位和接近四电子的转移过程。NG中掺杂氮原子的键合方式通过XPS进行表征,结果表明起始电位的高低取决于石墨氮含量。此外,所有表征结果表明总氮含量与氧还原反应性能没有直接关系。     

KH-570功能化石墨烯的制备与表征

采用Hummers法对天然石墨进行氧化处理制备了氧化石墨烯,通过γ-甲基丙烯酰氧丙基三甲氧基硅烷与氧化石墨烯反应得到功能化氧化石墨烯,然后在水合肼的作用下制备了功能化石墨烯。未烘干的功能化石墨烯在超声处理下,能稳定分散在体积比为9∶1(V/V)的乙醇/水、丙酮/水或N,N-二甲基甲酰胺/水的混合溶剂中。用傅立叶变换红外光谱、原子力显微镜、X射线光电子能谱及X射线衍射对样品结构、形貌进行了分析。结果表明,KH-570上的硅氧烷与氧化石墨烯上的羟基发生了反应,经水合肼还原后,功能化石墨烯的无序度增加,层间距也比功能化氧化石墨烯的缩小了。功能化石墨烯在DMF/水中呈高度剥离状态,片层厚度为1.1～2.3 nm。     

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.     

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/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。     

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.     

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.     

微波溶剂热法制备掺氮石墨烯用于碱性氧还原反应

采用微波处理氧化石墨烯（GO）与乙二醇（EG）、乙二胺（ED）混合液的方法制备氮掺杂石墨烯（NG）,使用旋转圆盘电极对NG催化氧还原在碱性溶液中反应进行研究,并考察了不同微波辐射时间、ED与EG之比对反应性能的影响。采用X射线衍射仪（XRD）、透射电子显微镜（TEM）、拉曼光谱（Raman）和傅里叶变换红外光谱（FT-IR）研究了NG催化剂的结构与性质。相比于未掺氮的石墨烯样品,NG表现出更正的起始电位和接近四电子的转移过程。NG中掺杂氮原子的键合方式通过XPS进行表征,结果表明起始电位的高低取决于石墨氮含量。此外,所有表征结果表明总氮含量与氧还原反应性能没有直接关系。     

High-density amine-terminated monolayers formed on fluorinated CVD-grown graphene

There has been considerable interest in chemically functionalizing graphene films to control their electronic properties, to enhance their binding to other molecules for sensing, and to strengthen their interfaces with matrices in a composite material. Most reports to date have largely focused on noncovalent methods or the use of graphene oxide. Here, we present a method to activate CVD-grown graphene sheets using fluorination followed by reaction with ethylenediamine (EDA) to form covalent bonds. Reacted graphene was characterized via X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and Raman spectroscopy as well as measurements of electrical properties. The functionalization results in stable, densely packed layers, and the unbound amine of EDA was shown to be active toward subsequent chemical reactions.     

KOH-activated nitrogen-doped graphene by means of thermal annealing for supercapacitor

KOH-activated nitrogen-doped graphene nanosheets (aNG) have been synthesized using thermal annealing method and applied in supercapacitor. The samples are characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and electrochemical techniques. Electrochemical results show that a capacitance of 132.4 F g^?1 at a charge/discharge current density of 0.1 A g^?1 is obtained for KOH-activated nitrogen-doped graphene which is nearly five times larger than that without KOH treatment. The present work demonstrates that KOH activation of thermally annealed nitrogen-doped graphene is a promising method for enhancing its application in energy storage system.     

Graphene Supported Platinum Nanoparticles as Catalyst for Oxygen Reduction Reaction

Graphene supported Pt nanoparticles were fabricated via electrochemical reduction method and the application of them in oxygen reduction reaction was also investigated. The results of field emission scanning electron microscope(SEM), X-ray photoelectron spectroscopy(XPS) and Raman spectroscopy reveal that the interaction between Pt nanoparticles and graphene sheets can prevent graphene from agglomeration and improve the electronic conductivity of the composite. And the graphene supported Pt nanoparticles exhibit excellent electrocatalytic activity toward oxygen reduction reaction.     

Synthesis of Nitrogen-Doped Graphene via Thermal Annealing Graphene with Urea

Chemical doping is an effective method to intrinsically modify the chemical and electronic property of graphene. We propose a novel approach to synthesize the nitrogen-doped graphene via thermal annealing graphene with urea, in which the nitrogen source can be controllably released from the urea by varying the annealed temperature and time. The doped N content and the configuration N as well as the thermal stabilities are also evaluated with X-ray photoelectron spectroscopy and Raman spectra. Electrical measurements indi-cate that the conductivity of doped graphene can be well regulated with the N content. The method is expected to produce large scale and controllable N-doped graphene sheets for a variety of potential applications.     

Effect of nitrogen doping on hydrogen storage capacity of palladium decorated graphene

A high hydrogen storage capacity for palladium decorated nitrogen-doped hydrogen exfoliated graphene nanocomposite is demonstrated under moderate temperature and pressure conditions. The nitrogen doping of hydrogen exfoliated graphene is done by nitrogen plasma treatment, and palladium nanoparticles are decorated over nitrogen-doped graphene by a modified polyol reduction technique. An increase of 66% is achieved by nitrogen doping in the hydrogen uptake capacity of hydrogen exfoliated graphene at room temperature and 2 MPa pressure. A further enhancement by 124% is attained in the hydrogen uptake capacity by palladium nanoparticle (Pd NP) decoration over nitrogen-doped graphene. The high dispersion of Pd NP over nitrogen-doped graphene sheets and strengthened interaction between the nitrogen-doped graphene sheets and Pd NP catalyze the dissociation of hydrogen molecules and subsequent migration of hydrogen atoms on the doped graphene sheets. The results of a systematic study on graphene, nitrogen-doped graphene, and palladium decorated nitrogen-doped graphene nanocomposites are discussed. A nexus between the catalyst support and catalyst particles is believed to yield the high hydrogen uptake capacities obtained.     

金红石相TiO2-石墨烯复合材料的制备及其光催化性能

以鳞片石墨为原料, 用改进的Hummers法制备氧化石墨烯(GO), 以异丙醇钛为钛源经一步水热法制备得到金红石相TiO₂-石墨烯复合材料(rGO-TiO₂), 考察了氧化石墨烯用量对复合材料光催化性能的影响. 采用X射线衍射(XRD), 比表面积(BET), 透射电镜(TEM), 扫描电镜(SEM), 拉曼光谱, 紫外-可见(UV-Vis)吸收光谱和荧光光谱(PL)等测试手段对复合材料进行表征. 结果表明: 复合材料中TiO₂为针簇状结构的金红石相, 与石墨烯能够均匀复合; 与纯金红石相TiO₂相比, 复合材料具有较大的比表面积. 研究了该复合材料在紫外光下对罗丹明B 以及可见光下对甲基橙光降解效果. 当氧化石墨烯浓度为0.5 mg·mL^-1时, 制备得到的复合材料rGO-TiO₂具有较好的光催化效果.     

Physical properties of silicone foams filled with carbon nanotubes and functionalized graphene sheets

Free-rising silicone foams were made with loading fractions of up to 0.25 wt.-% functionalized graphene sheets (FGS) and up to 1.0 wt.-% carbon nanotubes (CNTs) using hydrogen as blowing agent. Scanning electron microscopy of the samples revealed an open cellular structure and a homogeneous dispersion of both types of nanofillers. The incorporation of nanofiller affected the foaming process and thus the final foam density and cellular structure. Transmission electron microscopy revealed the formation of a CNT network throughout the sample, while FGS presented an exfoliated and intercalated dispersion. The thermal stability of the samples was drastically affected by the presence of both nanofillers. Both nanofillers showed a positive effect on the compressive response of the foams. However, the nanocomposite foams were found to decrease the acoustic absorption with nanofiller content probably due to the variable foam structure and improved stiffness.