Effect of electrolytes on electrochemical properties of graphene sheet covered with polypyrrole thin layer

Graphene sheet (GS) was successfully covered with a polypyrrole (PPy) thin layer through in situ chemical oxidative polymerization of pyrrole monomers in aqueous solution by using GS as a support material and ferric trichloride as an oxidant. The resulting nanocomposite was studied by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) and electrical measurements, including cyclic voltammetry (CV), galvanostatic charge/discharge experiment (GCD), and impedance spectroscopy (EIS). It has been found that the nanocomposite exhibited a typically curved and layer–like structure, and conformational change of PPy chains occurred due to the π–π stacking interaction between the graphitic structures in GS and aromatic rings of the PPy chains. More attention was paid to the effect of electrolytes on electrochemical properties of the nanocomposites, as expected, electrochemical performance was dependent on the nature of the electrolyte, and the neutral electrolytes containing alkali metal ions were found to be very suitable for GS/PPy nanocomposite. Compared with the pure PPy, the nanocomposite possessed larger specific capacitance and lower internal impedance, indicating that the nanocomposite can be a promising candidate as electrode material for supercapacitors.     

Effect of feeding ratios on the structure and electrochemical performance of graphite oxide/polypyrrole nanocomposites

Graphite oxide (GO)/polypyrrole (PPy) nanocomposites (GPYs) were synthesized using in situ polymerization.The effect of the feeding ratios of pyrrole and GO on the structure and electrochemical performances of GPYs was investigated.The structure was characterized via Fourier-transform infrared spectroscopy,scanning electron microscopy,transmission electron microscopy and X-ray diffraction.The electrochemical performance was characterized via cyclic voltammetry,galvanostatic charge-discharge and electrochemical impedance spectroscopy.The results indicate that the more pyrrole is added to GO (with GO concentrations of 20% and 50%),the more agglomeration of both PPy and GO layers occurs.This is detrimental to the capacitance utilization of PPy.When the feeding ratio of GO:pyrrole is 80:20,PPys with nanofibrils are dispersed homogenously in/on the exfoliated layer of GO and the conductivity is enhanced.The capacitance utilization of PPy in a composite with a GO concentration of 80% (383 F/g) is higher than that of pure PPy (201 F/g),which indicates the presence of a synergistic effect between GO and PPy.     

γ射线还原的氧化石墨烯的电学、热学和电化学性能

The properties of γ-ray-reduced graphene oxide samples (GRGOs) were compared with those of hydrazine hydrate-reduced graphene oxide (HRGO). Fourier transform infrared spectroscopy, X-ray diffractometry, Raman spectroscopy, Brunauer–Emmett–Teller surface area analysis, thermogravimetric analysis, electrometry, and cyclic voltammetry were carried out to verify the reduction process, structural changes, and defects of the samples, as well as to measure their thermal, electrical, and electrochemical properties. Irradiation with γ-rays distorted the structure of GRGOs and generated massive defects through the extensive formation of new smaller sp2-hybridized domains compared with those of HRGO. The thermal stability of GRGOs was higher than that of HRGO, indicating the highly efficient removal of thermally-labile oxygen species by γ-rays. RRGO prepared at 80 kGy showed a pseudocapacitive behavior comparable with the electrical double-layer capacitance behavior of HRGO. Interestingly, the specific capacitance of GRGO was enhanced by nearly three times compared with that of HRGO. These results reflect the advantages of radiation reduction in energy storage applications.     

Electrochemical reduction of graphene oxide films: Preparation, characterization and their electrochemical properties

Graphene oxide (GO) film was electrochemically reduced by a cyclic voltammetry technique in 6 mol L-1 KOH aqueous solution.Electrochemically reduced graphene oxide (ER-GO) film was characterized by X-ray diffraction,X-ray photoelectron spectroscopy,atomic force microscopy,and Raman spectroscopy.The oxygen content (with the O/C atomic ratio of 1.29%) was significantly decreased after electrochemical reduction.The ER-GO film exhibited a specific capacitance of 152 F g-1 at the current density of 5 A g-1 and a good rate capability.Furthermore,the ER-GO film showed an excellent cycling ability.The capacitance retention remained 99% after 3000 cycles at the current density of 10 A g-1.     

S/石墨烯复合材料的水热法制备及其电化学性能研究

采用水热法制备了S/石墨烯复合材料,并利用XRD,SEM,TEM等手段考察了其微观结构及形貌特征,发现石墨烯呈现多层状,与硫复合后能将其充分包覆。以复合材料为正极、锂为负极组装成扣式电池进行CV,EIS及充放电等电化学性能测试。结果表明:添加石墨烯后硫正极的可逆性明显改善,多次充放电后电池内阻有所增加,在0.3mA/cm2电流密度下放电,首次放电比容量为1 145mAh/g,经30次充放电循环后仍可稳定在500mAh/g。     

不同锂盐电解液对磷酸亚铁锂电化学性能的影响研究

目的研究LiFePO4在不同锂盐电解液体系中的电化学性能。方法采用恒电流充电、放电和循环伏安方法来进行相关研究。结果在不同锂盐(LiClO4、LiBF4以及LiPF6)和不同碳酸酯混合溶剂(EC-DEC、EC-DMC或者PC-DMC)所组成的电解液中,电极材料在1 M LiClO4/EC-DMC和1 M LiPF6/EC-DMC电解液中的电化学性能较好。其中在1 M LiClO4/EC-DMC电解液中充放电容量最高,而在1 M LiBF4/EC-DMC电解液中的充电、放电容量最低。结论锂盐本身及电解液的电导率对磷酸亚铁锂电化学性能有较大的影响。     

三维炭/还原氧化石墨烯纳米片的制备及其电化学性能

采用水热合成法,将间苯二酚甲醛树脂涂覆在还原氧化石墨烯片层上,经冷冻干燥及炭化后构筑三维炭/还原氧化石墨烯纳米片。使用SEM、TEM、FTIR、XPS等对样品的形貌与结构进行表征,利用循环伏安、恒流充放电及电化学阻抗法测试了样品的电化学性能。结果表明,间苯二酚甲醛树脂成功将还原氧化石墨烯片包覆,二者构筑的三维炭/还原氧化石墨烯复合纳米片厚度为25nm;当循环伏安测试扫描速率为20mV/s时,三维炭/还原氧化石墨烯纳米片电极材料的比电容分别为还原氧化石墨烯与间苯二酚甲醛树脂炭电极材料相应值的1.8和2.8倍;在0.2A/g的充电电流密度下,三维炭/还原氧化石墨烯纳米片电极材料比电容为154.4F/g。     

手性石墨烯薄膜拉伸力学性能分子动力学研究

基于分子动力学方法,用Tersoff势函数描述碳原子性质,研究了手性取向对石墨烯薄膜拉伸力学性能的影响。通过构建不同手性的石墨烯薄膜模型,在周期性边界条件下采用NVT系综,以变形方式分别对不同手性的石墨烯薄膜施加均匀应变,模拟了拉伸变形条件下手性石墨烯薄膜的破坏过程,得到了相应的应力-应变关系以及拉伸破坏形态。结果表明,不同的手性取向对石墨烯薄膜的杨氏模量影响不明显,拉伸强度随着手性角度的增大先迅速减小再逐渐增大,其拉伸极限应变随着手性角度的增大整体呈减小趋势。     

石墨烯/二氧化锰复合材料的制备及其电化学性能

通过水热法在160℃条件下成功制备了手风琴状石墨烯/MnO2复合材料.通过场发射扫描电镜、透射电镜、X射线衍射、X射线能量色散谱、BET法以及拉曼光谱对材料进行表征.结果表明,手风琴状二氧化锰与层状石墨烯之间具有十分高效的贴合,这种创新性设计有效地利用了石墨烯的高电导率、大比表面积以及二氧化锰的优秀赝电容行为.电化学测试结果给出在0.2 A·g-1时,样品的比电容高达138 F·g-1,数倍增强于单独的二氧化锰或石墨烯样品.     

Mechanism of intercalation and deintercalation of lithium ions in graphene nanosheets

Graphene nanosheets (GNSs) were synthesized by reducing exfoliated graphite oxides. Their structure, surface morphology and lithium storage mechanism were characterized and investigated systematically using X-ray diffraction, atomic force microscopy, scanning electron microscopy, charge-discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. It was found that the GNSs, which were obtained via chemical synthesis, were primarily less than 10 graphene layers. The GNS electrodes, which were fabricated from the reduced GNSs, exhibited an enhanced reversible lithium storage capacity and good cyclic stability when serving as anodes in lithium-ion batteries. Also, the first-cycle irreversible capacities of the system were relatively high, because of the formation of a solid electrolyte interphase film on the surface of the GNS electrode and the spontaneous stacking of GNSs during the first lithiation. The electrochemical impedance spectroscopy results suggest that the solid electrolyte interphase film on the GNS electrode during first lithiation were primarily formed at potentials between 0.95 and 0.7 V. Also, the symmetry factor of the charge transfer was measured to be 0.446.     

GO/PPy/Pb3O4修饰电极的制备及其在电化学传感中的应用

通过制备氧化石墨烯/聚吡咯/四氧化三铅(GO/PPy/Pb₃O₄)复合材料,用于构建电化学传感器,以实现对对苯二酚的电化学检测。通过利用π-π共轭效应,实现吡咯单体在氧化石墨烯表面的原位聚合。以GO/PPy纳米复合材料为基底,通过水热反应制备得到具有微/纳结构的GO/PPy/Pb₃O₄复合材料。以扫描电镜(SEM),傅里叶红外(FTIR)和X射线衍射(XRD)等对复合材料进行表征,用差分脉冲伏安法研究对苯二酚在修饰电极上的电化学行为。通过对比不同修饰电极的电化学传感性能,发现GO/PPy/Pb₃O₄修饰电极展示了良好的导电性和优异的电催化性能。结果表明,该电化学传感器在1.0~35 μg/L范围内与其氧化峰电流呈良好的线性关系,其检测限为0.3 μg/L。此外,该电化学传感器还具有良好的重现性和稳定性。     

弯曲对扶手椅型石墨烯纳米带电子性质的影响

石墨烯纳米带并不是一个完全平整的结构,而是一个准平面结构．为了研究非平整对石墨烯纳米带电子结构的影响,利用紧束缚方法和轨道杂化理论,研究了弯曲对扶手椅型石墨烯纳米带电子结构的影响．计算结果表明：扶手椅型石墨烯纳米带电子性质与弯曲的程度有关,且在高能部分影响较大;当纳米带的宽度一定时,随着弯曲程度的增加,能带的带隙随之增加．     

A review on hybridization modification of graphene and its polymer nanocomposites

Recently,graphene has attracted numerous interests from both fundamental and applied fields due to its excellent mechanical,thermal,electrical conductivity and other novel properties.This review gives an overview of recent progress on hybridization modifications of graphene with carbon nanomaterials.Some example applications of graphene-based nanohybrids in polymer composites,optical and conducting materials,high performance electrolyte materials and as well as other functional materials are summarized and discussed.     

聚吡咯/聚砜复合膜的电化学制备及其电化学性能

采用电化学聚合法制备了聚吡咯（PPY）／聚砜（PSF）复合膜，分别用扫描电子显微镜（SEM）和红外光谱（FT—IR）表征了复合膜的表面形态和化学组分，并用循环伏安法和电化学交流阻抗法对其电化学性能进行了研究．结果表明，复合膜呈双层不对称孔结构，其内层（与工作电极接触的一面）是由黑色聚吡咯组成的带少量微孔的致密导电层，而外层（与溶液接触的一面）则是由白色聚砜组成的具有许多微孔的绝缘层；相同条件下所制的复合膜电化学重复性好，在酸性溶液中具有较好的电化学稳定性和电化学活性．     

石墨烯对铜纳米复合材料物理力学性能和摩擦学性能的影响

本文对铜–石墨烯纳米片（GN）纳米复合材料的力学性能和摩擦学性能进行了实验研究。我们采用化学包覆法将银粒子包覆在GNs上,以避免其与铜的反应和金属间相的形成。分析了GN含量对制备的纳米复合材料的结构、力学性能和摩擦学性能的影响。结果表明,化学镀是一种有效避免铜与碳反应和金属间相形成的方法。GNs的加入显著提高了Cu纳米复合材料的力学性能和摩擦学性能。然而,GNs的添加需要谨慎进行,因为在达到一定的阈值后,其机械性能和摩擦学性能会受到负面影响。结果表明,GN含量为0.5vol%时,复合材料的硬度、磨损率和摩擦系数分别比铜纳米复合材料提高了13%、81.9%和49.8%。这些改进的性能是由于降低的晶体尺寸,GNs的存在,以及复合材料成分的均匀分布。     

退火工艺对薄规格SPCC钢板组织和性能的影响

通过罩式退火模拟试验,研究退火温度和保温时间对0.3 mm厚的薄规格SPCC钢板组织及性能的影响,分析其织构随退火温度的变化规律.结果表明,经过680℃×13h退火,薄规格SPCC钢板的HV值为77.45,断后延伸率A50为45.6％;随着退火温度的升高,SPCC钢板的晶粒尺寸逐渐增大,硬度和延伸率逐渐降低;随着保温时间的延长,钢板的晶粒尺寸和延伸率略有增大,硬度有所降低,但变化幅度均较小,保温时间对薄规格SPCC钢板深冲性能的影响较小;680℃和700℃退火后,SPCC钢板的织构组分集中分布在γ取向线上,随着退火温度的升高,变形织构{112}<110>强度降低,有利织构{111}<112>强度提高.     

[Pmim][ClO_4]电解质的物化性质及其在超级电容器中的性能研究

采用两步法设计合成了一种新型离子液体电解质(液)1-戊基-3-甲基咪唑高氯酸盐([Pmim][Cl O4]),对这种电解质的密度、表面张力、电导率等物化性质进行了测定.并将其与活性炭电极组装成超级电容器,通过交流阻抗、循环伏安及恒流充放电等测试手段对其电化学性能进行了研究.测试结果表明,该离子液体的密度和表面张力都随温度升高而减小,超级电容器的电化学窗口可以达到5.0 V,并且具有良好的电容特性、可逆性及循环特性,是一种具有应用潜力的超级电容器电解液.     

石墨烯对气压烧结WC-Co硬质合金性能的影响

为了减小氧化石墨烯（graphene oxide,GO）在WC-10Co硬质合金中的团聚以及高温液相烧结过程中Co对GO的溶蚀作用,通过化学镀的方式制备了改性氧化石墨烯（GO/Ni）,随后利用静电吸附以及机械搅拌两种方法分别制备了WC-10Co-GO复合粉体和WC-10Co-GO/Ni复合粉体。用扫描电子显微镜（scanning electron microscope,SEM）和透射电子显微镜(transmission electron microscope,TEM)对改性后的GO以及复合粉体进行微观形貌的表征。采用气压烧结工艺制备了WC-10Co、WC-10Co-GO和WC-10Co-GO/Ni硬质合金并研究了硬质合金的物理性能和力学性能。实验结果表明：随着GO和GO/Ni的加入,硬质合金的密度和洛氏硬度有了略微的降低;对比WC-10Co硬质合金,WC-10Co-GO和WC-10Co-GO/Ni硬质合金的横向断裂强度分别提升了35.2%和59.7%,其中GO/Ni作为作为基体增强相的效果最佳。     

聚吡咯H+选择电极的性能研究

采用电化学合成方法制备了聚吡咯H^ 选择电极．利用红外光谱探讨了掺杂不同阴离子聚吡咯膜的结构特征;探讨了聚吡咯电极在pH缓冲溶液中的阻抗谱特征及pH响应机理．比较了各种电极的能斯特斜率、转换系数和温度效应的差异,实验结果表明,未掺杂的聚吡咯(Pt／PPy)对H^ 响应的能斯特斜率、转换系数较掺杂T5O^-离子[Pt／PPy(T5O^-)]和HCO3^-离子[Pt／PPy(HCO3^-)]的要大．     

Preparation of graphene and TiO2 layer by layer composite with highly photocatalytic efficiency

A process for fabricating graphene and TiO2 layer by layer composite was introduced to improve the photocatalytic activity by controlling the layers, thickness and the mass ratio between graphene and TiO2. The graphene oxide (GO) was synthesized from natural graphite pow der by the modified Hummers met hod. Large-area uniform GO and TiO2 thin films were made by a spin-coating process in turn. After exposure of the TiO2/GO multilayer film to UV light irradiation which allows the reduction of GO to graphene, a novel photocatalyt ic structure as graphene and TiO2 layer by layer composite was synthesized. The cross-sectional SEM image showed that a clear layer by layer microstructure with a single layer thickness of graphene or TiO2 was in the range of about 50 nm. The total thickness of the film was around 5 μm which was varied according to the layer number of spin coating process. Raman spectra revealed th at significant structural changes occurred through UV light irradiation. Photodegrada tion for methylene blue (MB) exhibited that the layer by layer com posite is of higher photocatalytic activity than the pure TiO2 layer.