石墨烯的微波法制备及其电化学电容性能的研究

以天然鳞片石墨为原料,采用改进的Hummers方法制备了氧化石墨,然后通过微波剥离还原氧化石墨制备了石墨烯,并利用红外光谱、扫描电镜和透射电镜对其进行了表征。以所制石墨烯为电极材料、1 mol/L的TEMABF4/PC为电解液制备了超级电容器,并对其电化学性能进行了研究。结果表明:经过微波剥离,氧化石墨的含氧基团已基本完全分解,所得石墨烯为表面具有大量褶皱的薄层。所制电容器具有良好的电容性能,在扫描速度为10 mV/s情况下,其单电极比容量为102 F/g,比能量则高达22.1 Wh/kg。     

PANi/PPy/GO复合材料的制备与电化学性能

利用两步原位聚合法制备聚苯胺/聚吡咯/氧化石墨烯(PANi/PPy/GO)复合材料,考察了苯胺/吡咯/GO原料比对复合材料结构、微观形貌及电化学性能的影响。结果表明,PPy和PANi分别以非晶态形式均匀地原位复合在GO和PPy/GO片的表面; PANi/PPy/GO复合材料主要是靠法拉第赝电容进行电荷存储,且比电容较大、电荷转移电阻较小、循环稳定性较高;当苯胺/吡咯/GO原料质量比为10∶5∶1时,所制备复合材料利用循环伏安法和恒电流充放电法计算的比电容分别达到最大值154.7和243.3 F·g~(-1)。PANi/PPy/GO复合材料可用于超级电容器的电极材料。     

CaMoO4/GO复合材料的制备及其超级电容器性能

采用水热法成功合成了CaMoO₄/氧化石墨烯(GO)纳米复合材料。通过材料的表面形貌、晶体结构和电化学性能研究合成的纳米复合材料。结果表明,CaMoO₄/GO电极在电流密度0.5 A/g时比电容高达571.82 F/g,并且在1 A/g的电流密度下,经过1000次循环后的比电容保持率仍为84%。为了测试电极材料的实际应用效果,全固态超级电容器(ASC)分别使用CaMoO₄/GO和活性炭(AC)作为正极和负极进行组装。组装的ASC在功率密度1710.3 W/kg下显示出25.18 W·h·kg^-1的能量密度,并且能通过串联4个ASC为红色发光二极管供电。上述结果表明CaMoO₄/GO电极材料在高性能储能设备的应用中具有非常大的潜力。     

石墨烯微波制备的改进及其电化学性能研究

为寻找高效、环保的方法制备出性能优异的石墨烯超级电容器电极,采用制备氧化石墨的改进法得到酸、中性氧化石墨(S-GO、Z-GO),经微波膨胀得到不同形貌的石墨烯纳米片(WS-GO和WZ-GO),对WS-GO活化得样品HWS-GO;通过SEM、FT-IR和电化学工作站对样品的形貌、组成和电化学性能进行表征分析。结果显示:WS-GO比电容可达222 F/g,可逆性好,商业应用潜力大。     

石墨烯微波制备的改进及其电化学性能研究

为寻找高效、环保的方法制备出性能优异的石墨烯超级电容器电极,采用制备氧化石墨的改进法得到酸、中性氧化石墨(S-GO、Z-GO),经微波膨胀得到不同形貌的石墨烯纳米片(WS-GO和WZ-GO),对WS-GO活化得样品HWS-GO;通过SEM、FT-IR和电化学工作站对样品的形貌、组成和电化学性能进行表征分析。结果显示:WS-GO比电容可达222 F/g,可逆性好,商业应用潜力大。     

超级电容器用竹炭的制备及其电容性能

以竹材为原料,在高温Ar保护下制备了高比表面积超级电容器用竹炭材料。用XRD和SEM对所制竹炭进行了物相分析和形貌观察;用循环伏安、恒电流充放电和交流阻抗谱研究了炭化温度对所制超级电容器性能的影响。结果表明:所得竹炭为无定形结构,随着炭化温度的升高,竹炭中石墨微晶向有序态结构发展。炭化温度为500℃时,制备的竹炭电性能最佳。在125mA/g电流密度下的首次放电比电容为226F/g;即使在500mA/g的大电流密度下,其放电比电容仍高达184F/g,第1000次循环时其放电比电容为138F/g,每次循环电容衰减仅为0.046F/g。     

氧化钌及其复合电极的制备与性能

在三氯化钌(RuCl3)水溶液中,采用循环伏安法在铜电极表面电沉积氧化钌(RuO2)作为超级电容器电极材料。为了提高材料的电化学性能,在电沉积液中引入了氧化石墨烯(GO)水溶液,制备出RuO2/GO复合电极。采用扫描电镜(SEM)观察两种电极的表面形貌,发现氧化钌及其复合电极经60℃干燥处理1 h后,颗粒更均匀且存在明显的多孔特征,电极材料具有良好的表面特性。电化学测试结果表明,扫描速度为0.1 V/s、工作电位窗口为1 V时,两种电极比电容分别为636.5和938 F/m2,功率密度分别为31.83和46.9 W/m2。因此,RuO2/GO复合电极具有较好的电容特性,适合用作超级电容器电极材料。     

Synthesis of carbon nanoparticle ionic liquid hybrids and the application in supercapacitor

以1-甲基-3-乙基咪唑四氟硼酸离子液体和果糖为原料,微波作用下一步制得一种新型碳点离子液体复合物,用此复合物代替部分导电剂和粘结剂制成新型炭基超级电容器,并与传统的炭基超级电容器进行了比较研究.结果表明:所制复合物中有大量直径小于4nm的碳纳米粒子,70℃时电导率达到13.26×10-3S·cm-1,所制超级电容器充放电效率由传统炭基超级电容器的89.1％提高到97.3％,比电容由115.7 F·g-1提高到251.1 F·g-1,内阻由1.95 Ω降低为1.23 Ω,且循环性能显著提高.     

碳点离子液体复合物的制备及其在超级电容器中的应用

以1-甲基-3-乙基咪唑四氟硼酸离子液体和果糖为原料,微波作用下一步制得一种新型碳点离子液体复合物,用此复合物代替部分导电剂和粘结剂制成新型炭基超级电容器,并与传统的炭基超级电容器进行了比较研究。结果表明:所制复合物中有大量直径小于4nm的碳纳米粒子,70℃时电导率达到13.26×10–3S·cm–1。所制超级电容器充放电效率由传统炭基超级电容器的89.1%提高到97.3%,比电容由115.7 F.g–1提高到251.1 F·g–1,内阻由1.95Ω 降低为1.23Ω ,且循环性能显著提高。     

石墨烯改性超级活性炭的制备及其在双电层电容器中的应用

采用复合/共活化的方法成功制备了石墨烯改性超级活性炭,并重点研究了复合工艺中氧化石墨烯和石油焦复合比对石墨烯改性超级活性炭性能的影响。当氧化石墨烯和石油焦的质量比为5:1000时效果最优,所制活性炭质量比电容为38.64 F/g,在85℃/2.85 V恒压充电32 h后容量衰减率为14.29%,明显优于纯活性炭。综合测试结果表明,石墨烯改性超级活性炭相较于纯活性炭,其比容量、内阻和稳定性均得到了改善。     

Nitrogen‐Doped Nanoporous Carbon/Graphene Nano‐Sandwiches: Synthesis and Application for Efficient Oxygen Reduction

A zeolitic‐imidazolate‐framework (ZIF) nanocrystal layer‐protected carbonization route is developed to prepare N‐doped nanoporous carbon/graphene nano‐sandwiches. The ZIF/graphene oxide/ZIF sandwich‐like structure with ultrasmall ZIF nanocrystals (i.e., ≈20 nm) fully covering the graphene oxide (GO) is prepared via a homogenous nucleation followed by a uniform deposition and confined growth process. The uniform coating of ZIF nanocrystals on the GO layer can effectively inhibit the agglomeration of GO during high‐temperature treatment (800 °C). After carbonization and acid etching, N‐doped nanoporous carbon/graphene nanosheets are formed, with a high specific surface area (1170 m² g^?1). These N‐doped nanoporous carbon/graphene nanosheets are used as the nonprecious metal electrocatalysts for oxygen reduction and exhibit a high onset potential (0.92 V vs reversible hydrogen electrode; RHE) and a large limiting current density (5.2 mA cm^?2 at 0.60 V). To further increase the oxygen reduction performance, nanoporous Co‐N_x/carbon nanosheets are also prepared by using cobalt nitrate and zinc nitrate as cometal sources, which reveal higher onset potential (0.96 V) than both commercial Pt/C (0.94 V) and N‐doped nanoporous carbon/graphene nanosheets. Such nanoporous Co‐N_x/carbon nanosheets also exhibit good performance such as high activity, stability, and methanol tolerance in acidic media.     

Red photoluminescence BCNO synthesized from graphene oxide nanosheets

In this paper, we demonstrate the conversion of graphene oxide (GO) into boron carbon oxynitride (BCNO) hybrid nanosheets via a reaction with boric acid and urea, during which the boron and nitrogen atoms are incorporated into graphene nanosheets. The experimental results reveal that GO is important for the photoluminescence (PL) BCNO phosphor particles. More importantly, in this system, the prepared BCNO phosphors can be used to prepare the materials needed for red light emitting diodes (LEDs).     

Tunable Nanochannels along Graphene Oxide/Polymer Core–Shell Nanosheets to Enhance Proton Conductivity

Simultaneous manipulation of topological and chemical structures to induce ionic nanochannel formation within solid electrolytes is a crucial but challenging task for the rational design of high‐performance electrochemical devices including proton exchange membrane fuel cell. Herein, a novel generic approach is presented for the construction of tunable ion‐conducting nanochannels via direct assembly of graphene oxide (GO)/poly(phosphonic acid) core–shell nanosheets prepared by surface‐initiated precipitation polymerization. Using this simple and rapid approach to engineer GO/polymer nanosheets at the molecular‐level, ordered and continuous nanochannels with interconnected hydrogen‐bonded networks having a favorable water environment can be created. The resulting membranes exhibit proton conductivities up to 32 mS cm^?1 at 51% relative humidity, surpassing state‐of‐the‐art Nafion membrane and all previously reported GO‐based materials.     

Greener Electrochemical Synthesis of High Quality Graphene Nanosheets Directly from Pencil and its SPR Sensing Application

A green, simple, and cost effective electrochemical method to synthesize pure graphene oxide (GO) and graphene nanosheets (GNs) using pencil in ionic liquid medium is reported. The morphology and microstructure of prepared GNs and GO are examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X‐ray diffraction (XRD), and Raman spectroscopy; the experiments confirm the formation of high quality graphene. The synthesized GO is used for the real‐time and label‐free surface plasmon resonance (SPR) sensing of the biological warfare agent Salmonella typhi.     

Multilayer Hybrid Films Consisting of Alternating Graphene and Titania Nanosheets with Ultrafast Electron Transfer and Photoconversion Properties

Alternating graphene (G) and titania (Ti_0.91O₂) multilayered nanosheets are fabricated using layer‐by‐layer electrostatic deposition followed by UV irradiation. Successful assemblies of graphene oxide (GO) and titania nanosheets in sequence with polyethylenimine as a linker is confirmed by UV–vis absorption and X‐ray diffraction. Photocatalytic reduction of GO into G can be achieved upon UV irradiation. Ultrafast photocatalytic electron transfer between the titania and graphene is demonstrated using femtosecond transient absorption spectroscopy. Efficient exciton dissociation at the interfaces coupled with cross‐surface charge percolation allows efficient photocurrent conversion in the multilayered Ti_0.91O₂/G films.     

A High‐Performance Graphene Oxide‐Doped Ion Gel as Gel Polymer Electrolyte for All‐Solid‐State Supercapacitor Applications

A high‐performance graphene oxide (GO)‐doped ion gel (P(VDF‐HFP)‐EMIMBF₄‐GO gel) is prepared by exploiting copolymer (poly(vinylidene fluoride‐hexafluoro propylene), P(VDF‐HFP)) as the polymer matrix, ionic liquid (1‐ethyl‐3‐methylimidazolium tetrafluoroborate, EMIMBF₄) as the supporting electrolyte, and GO as the ionic conducting promoter. This GO‐doped ion gel demonstrates significantly improved ionic conductivity compared with that of pure ion gel without the addition of GO, due to the homogeneously distributed GO as a 3D network throughout the GO‐doped ion gel by acting like a ion “highway” to facilitate the ion transport. With the incorporation of only a small amount of GO (1 wt%) in ion gel, there has been a dramatic improvement in ionic conductivity of about 260% compared with that of pure ion gel. In addition, the all‐solid‐state supercapacitor is fabricated and measured at room temperature using the GO‐doped ion gel as gel polymer electrolyte, which demonstrates more superior electrochemical performance than the all‐solid‐state supercapacitor with pure ion gel and the conventional supercapacitor with neat EMIMBF₄, in the aspect of smaller internal resistance, higher capacitance performance, and better cycle stability. These excellent performances are due to the high ionic conductivity, excellent compatibility with carbon electrodes, and long‐term stability of the GO‐doped ion gel.     

Ultrathin free-standing graphene oxide film based flexible touchless sensor

Ultrathin free-standing graphene oxide (GO) films were fabricated by vacuum filtration method assisted with Ni(OH)2 nanosheets as the sacrifice layer.The surface of the obtained GO film is very clean as the Ni(OH)2nanosheets can be thoroughly etched by HC1.The thickness of the GO films can be well-controlled by changing the volume of GO dispersion,and the thinnest GO film reached ～12 nm.As a novel and transparent dielectric material,the GO film has been applied as the dielectric layer for the flexible touchless capacitive sensor which can effectively distinguish the approaching of an insulator or a conductor.     

Epoxy Toughening with Low Graphene Loading

The toughening effects of graphene and graphene‐derived materials on thermosetting epoxies are investigated. Graphene materials with various structures and surface functional groups are incorporated into an epoxy resin by in situ polymerization. Graphene oxide (GO) and GO modified with amine‐terminated poly(butadiene‐acrylonitrile) (ATBN) are chosen to improve the dispersion of graphene nanosheets in epoxy and increase their interfacial adhesion. An impressive toughening effect is observed with less than 0.1 wt% graphene. A maximum in toughness at loadings as small as 0.02 wt% or 0.04 wt% is observed for all four types of graphene studied. An epoxy nanocomposite with ATBN‐modified GO shows a 1.5‐fold improvement in fracture toughness and a corresponding 2.4‐fold improvement in fracture energy at 0.04 wt% of graphene loading. At such low loadings, these graphene‐type materials become economically feasible components of nanocomposites. A microcrack mechanism is proposed based on microscopy of the fracture surfaces. Due to the stress concentration by graphene nanosheets, microcracks may be formed to absorb the fracture energy. However, above a certain graphene concentration, the coalescence of microcracks appears to facilitate crack propagation, lowering the fracture toughness. Crack deflection and pinning likely contribute to the slow increase in fracture toughness at higher loadings.     

Highly Stable Graphene‐Based Multilayer Films Immobilized via Covalent Bonds and Their Applications in Organic Field‐Effect Transistors

Highly stable graphene oxide (GO)‐based multilayered ultrathin films can be covalently immobilized on solid supports through a covalent‐based method. It is demonstrated that when (3‐aminopropyl) trimethoxysilane (APTMS), which works as a covalent cross‐linking agent, and GO nanosheets are assembled in an layer‐by‐layer (LBL) manner, GO nanosheets can be covalently grafted on the solid substrate successfully to produce uniform multilayered (APTMS/GO)N films over large‐area surfaces. Compared with conventional noncovalent LBL films constructed by electrostatic interactions, those assembled using this covalent‐based method display much higher stability and reproducibility. Upon thermal annealing‐induced reduction of the covalent (APTMS/GO)N films, the obtained reduced GO (RGO) films, (APTMS/RGO)N, preserve their basic structural characteristics. It is also shown that the as‐prepared covalent (APTMS/RGO)N multilayer films can be used as highly stable source/drain electrodes in organic field‐effect transistors (OFETs). When the number of bilayers of the (APTMS/RGO)N film exceeds 2 (ca. 2.7 nm), the OFETs based on (APTMS/RGO)N electrodes display much better electrical performance than devices based on 40 nm Au electrodes. The covalent protocol proposed may open up new opportunities for the construction of graphene‐based ultrathin films with excellent stability and reproducibility, which are desired for practical applications that require withstanding of multistep post‐production processes.