纳米CuFe2O4-rGO复合材料的制备及电化学性能

采用溶剂热法成功制备了纳米CuFe₂O₄-rGO复合材料。通过X射线衍射（XRD）,扫描电子显微镜（SEM）、透射电子显微镜（TEM）和电化学工作站对样品的结构、形貌及电容特性进行表征。结果表明,CuFe₂O₄纳米粒子均匀地分散在石墨烯片层间,其中CuFe₂O₄-20% rGO复合材料具有最优的电化学性能,当电流密度1 A·g^-1时,其比电容为1 952.5 F·g^-1,当电流密度为1 A·g^-1时,CuFe₂O₄-20% rGO复合材料经1 000次充放电后的比电容保持率为86.17%。     

A DFT study of formaldehyde adsorption on functionalized graphene nanoribbons

Density functional theory (DFT) based ab initio calculations were done to monitor the formaldehyde (CHOH) adsorptive behavior on pristine and Ni-decorated graphene sheet. Structural optimization indicates that the formaldehyde molecule is physisorbed on the pristine sheet via partly weak van der Waals attraction having the adsorption energy of about −15.7 kcal/mol. Metal decorated sheet is able to interact with the CHOH molecule, so that single Ni atoms prefer to bind strongly at the bridge site of graphene and each metal atom bound on sheet may adsorb up to four CHOH. The findings also show that the Ni decoration on graphene surface results in some changes in electronic properties of the sheet and its E_g is remained unchanged after adsorption of CHOH molecules. It is noteworthy to say that no bond cleavage was observed for the adsorption of CHOH on Ni-decorated graphene.     

Opening Band Gap of Graphene by Chemical Doping: a First Principles Study

Single atom chemically doped graphene has been theoretically studied by density functional theory. The largest band gap, 0.62 eV, appears in arsenic atom doped graphene, then 0.60 eV comes by the tin atom, whose deformations can neither be ignored. It is also found that oxygen and iron single atom embedded graphene can open band gap by 0.52 and 0.54 eV, respectively. Moreover, doping O atom shows little distortion and high stability by charge redistribution. The band gap of Fe doped graphene is opened by orbital hybridization. The other heteroatom doped results are a little inferior to them.     

Switching effects in superconductor/ferromagnet/superconductor graphene junctions

The Josephson effect in the superconductor/ferromagnet/superconductor （SFS） graphene Josephson junction is studied using the Dirac Bogoliubov-de Gennes （DBdG） formalism. It is shown that the SFS graphene junction drives 0–π transition with the increasing of p=h0L/vF？, which captures the effects of both the exchange field and the length of the junction; the spin-down current is dominant. The 0 state is stable for p 〈 pc （critical value pc ≈ 0.80） and the π state is stable for p 〉 pc, where the free energy minima are at φg=0 and φg=π, respectively. The coexistence of the 0 and π states appears in the vicinity of pc.     

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。     

氮掺杂石墨烯的制备及其在化学储能中的研究进展

石墨烯独特的二维空间结构使其具有优异的导电性能、力学性能以及超大的比表面积,被认为是颇具潜力的新型储能材料,是目前储能研究的热点之一。 但是石墨烯易团聚、表面光滑且呈惰性而不利于与其它材料的复合,导致其应用受到限制。 石墨烯掺氮可改变其电子结构,增加表面的活性位,从而提高其应用于储能器件时的电化学性能。 本文综述了近几年氮掺杂石墨烯的制备方法以及其在超级电容器、锂离子电池、锂空电池以及锂硫电池等化学储能领域中的应用,指出了目前氮掺杂石墨烯在制备和储能应用中关注的核心问题,并对氮掺杂石墨烯的发展前景进行了展望。     

聚苯胺与还原石墨烯复合材料的微波吸收性能

采用化学氧化法制备聚苯胺与还原石墨烯复合材料。复合材料的结构、晶型和电磁参数分别通过X射线衍射仪及HP8722ES型矢量网络分析仪进行表征、测试与分析。结果表明,同聚苯胺相比,聚苯胺与还原石墨烯复合材料的介电损耗明显增加。而且在复合材料中,石墨烯的含量越大,材料的微波吸收性能越好,在频率波段（9.5~13.4GHz）反射损耗均小于-10 dB,并在频率为11.2 GHz时达到最大反射损耗-29.69 dB。聚苯胺与还原石墨烯的复合使得材料的载流子迁移率变大,吸波特性得到改善。     

The inelastic electron tunneling spectroscopy of edge-modified graphene nanoribbon-based molecular devices

The inelastic electron tunneling spectroscopy(IETS) of four edge-modified finite-size grapheme nanoribbon(GNR)-based molecular devices has been studied by using the density functional theory and Green's function method. The effects of atomic structures and connection types on inelastic transport properties of the junctions have been studied. The IETS is sensitive to the electrode connection types and modification types. Comparing with the pure hydrogen edge passivation systems, we conclude that the IETS for the lower energy region increases obviously when using donor–acceptor functional groups as the edge modification types of the central scattering area. When using donor–acceptor as the electrode connection groups, the intensity of IETS increases several orders of magnitude than that of the pure ones. The effects of temperature on the inelastic electron tunneling spectroscopy also have been discussed. The IETS curves show significant fine structures at lower temperatures. With the increasing of temperature, peak broadening covers many fine structures of the IETS curves.The changes of IETS in the low-frequency region are caused by the introduction of the donor–acceptor groups and the population distribution of thermal particles. The effect of Fermi distribution on the tunneling current is persistent.     

光抽运多层石墨烯太赫兹表面等离子体增益特性的研究

本文建立了光抽运多层石墨烯表面等离子体模型,计算了光抽运多层石墨烯等离子体传播系数的实部和吸收系数,讨论了动量弛豫时间、温度、层数、准费米能级对表面等离子体传播系数的实部和吸收系数的影响.研究结果表明,光抽运多层石墨烯使其动态电导率的实部在太赫兹频段内出现负值时,石墨烯表面等离子体实现增益.通过光抽运剥离层石墨烯和含有底层石墨烯结构表面等离子体传播系数和吸收系数比较,表明光抽运剥离层石墨烯能更有效地实现表面等离子体的增益.同时,在低温下,光抽运具有合适层数的石墨烯比光抽运单层石墨烯能获得更大的表面等离子体增益.     

First-principles study of lithium intercalated bilayer graphene

Lithium intercalated bilayer graphene has been investigated using first-principles density functional theory calculations. Results show that there exist AB and AA stacking sequences for bilayer graphene in which the latter is more favorable for the Li storage and the former will evolve into the latter with the intercalation of Li ions. The relationship between the interlayer distance of two graphene sheets and the intercalated capacity of Li ions is discussed. It is found that structural defect is identified to store Li ions more favorably than pristine bilayer graphene and an isolated C atom vacancy in bilayer graphene can capture three Li ions between two graphene sheets.