氮掺杂石墨烯纳米片的制备及其电化学性能

以石墨片为原料,在氮气气氛下,通过机械针磨法制备了氮掺杂石墨烯纳米片.扫描电子显微镜和比表面积分析表明机械针磨过程可以有效地将大尺寸石墨片破碎成石墨烯纳米片.在石墨片的破碎过程中,会引起C—C键的破坏.因此,在破坏的边缘位置能够产生碳活性点.这些碳活性点可以与氮反应实现氮元素的掺杂.X射线光电子能谱分析表明碳活性点与氮反应使氮元素掺入石墨烯结构边缘,形成吡咯型氮和吡啶型氮.电化学阻抗谱分析表明所制备的氮掺杂石墨烯纳米片对I_3~-还原反应具有较高的电催化活性,循环伏安与恒流充放电测试表明氮掺杂石墨烯纳米片具有较好的电容性能.较高的比表面积和边缘氮掺杂结构是氮掺杂石墨烯纳米片具有优异电化学性能的主要原因.因此,氮掺杂石墨烯纳米片可以应用于染料敏化太阳能电池对电极和超级电容器电极.     

碳、碳氮和硼碳氮纳米管场发射性能的比较研究

采用高温热解法在860℃分别制备出了碳、碳氮和硼碳氮纳米管，提纯后利用丝网印刷工艺分别将它们制备成薄膜，并测试了它们的场发射性能.结果表明：碳纳米管、碳氮纳米管和硼碳氮纳米管薄膜的开启电场分别为2.22，1.1和4.4V/μm，当电场增加到5.7V/μm时，它们的电流密度分别达到1400，3000μA/cm²和小于50μA/cm².碳和碳氮纳米管薄膜的场增强因子分别为10062和11521.可见，碳氮纳米管的场发射性能优于碳纳米管，而硼碳氮纳米管的场发射性能比前两者要差.解释了这三种纳米管场发射性能差别的原因. 关键词： 碳纳米管 碳氮纳米管 硼碳氮纳米管 场发射     

多孔碳纳米球的制备及其电化学性能

以三嵌段共聚物F108为软模板,通过水热法合成酚醛树脂球并在氮气氛围下碳化、KOH活化处理,最终得到多孔碳纳米球材料.通过扫描电子显微镜、透射电子显微镜和氮气吸附分析仪对样品进行表征,结果表明样品的平均粒径为120 nm,球形度高,比表面积达到1403 m~2/g,孔径分布广.通过X射线衍射研究样品的结晶度,傅里叶红外光谱分析样品表面官能团的情况,结果表明KOH处理和高温处理使得样品的微晶结构有序度提高,表面官能团含量降低.以多孔碳纳米球作为超级电容器电极的活性物质,电化学特性测试结果表明,多孔碳纳米球材料的比电容能够达到132 F/g(0.2 A/g),在10 A/g的电流密度下,经过10000次循环充放电后,电容量保留率为97.5%.本文采用水热法制备的多孔碳纳米球电化学性能良好,适用于超级电容器电极材料,研究结果表明,比表面积大、孔径分布合适(具有一定介孔含量)、结晶度高和含有少量表面官能团的理化特性的电极材料,其电化学性能更加优越.     

基于纳米压痕法的多孔硅硬度及杨氏模量与微观结构关系研究

采用电化学腐蚀制备多孔硅，利用场致发射扫描式电子显微镜(field emission scanning electron microscope，FESEM)观测多孔硅的二维微观形貌，利用Nano Indenter XP中的纳米轮廓扫描仪组件(nano profilometry, NP)得到其三维拓扑分析图像，分析了微观结构差异的原因并讨论了多孔硅内部微观结构对其机械性能的影响；利用MTS Nano Indenter XP纳米压入测量仪器，研究了多孔硅的显微硬度和杨氏模量随压入深度的变化规律，比较了不同孔隙率多孔硅的机械性能差别.实验结果测得40mA/cm²，60mA/cm²，80mA/cm²和100mA/cm²四个不同腐蚀电流密度条件下制备多孔硅样品的孔隙率在60%—80%范围内，孔隙率随着腐蚀电流密度的增加而增大；在氢氟酸(HF)浓度为20%的条件下制备出多孔硅样品的厚度在40μm—50μm范围内；测得多孔硅的平均硬度、平均杨氏模量分别在0.478GPa—1.171GPa和10.912GPa—17.15GPa范围内，并且其数值随腐蚀电流密度的增加而减小，在纳米硬度范围内随压入深度的增加而减小，在显微硬度范围内其数值保持相对恒定，分析了样品表面、厚度、微观结构，及环境对其机械性能的影响，得到了多孔硅力学性能随其微观尺度形貌的变化规律. 关键词： 多孔硅 微观结构 硬度 杨氏模量     

基于片层结构钴卟啉金属有机骨架的高效氧还原反应电催化剂

使用片层结构的金属有机骨架作为前驱物,通过高温煅烧制备出氮掺杂的介孔碳材料,同时在片层碳骨架上均匀分布着石墨化碳包裹的钴纳米粒子.电化学测试表明,800℃制备的样品具有与铂炭（Pt/C）催化剂相接近的氧还原反应催化活性,催化稳定性和甲醇耐受性良好,显著超越商品化Pt/C催化剂.     

铝氮共掺杂氧化锌纳米管电子结构的第一性原理研究

采用基于密度泛函理论的第一性原理计算, 对(6,0)单壁氧化锌纳米管、铝掺杂、氮掺杂和铝氮共掺杂纳米管的能带结构、态密度和差分电荷密度进行了研究. 结果表明, 氮掺杂可以在纳米管禁带中引入受主能级, 实现纳米管的p型掺杂, 但是受主能级局域性较强, 导致氮溶解度低. 引入铝元素可以有效降低氮形成受主能级局域性, 激活氮元素, 铝氮共掺杂有望成为氧化锌纳米管一种更为有效的p型掺杂方法. 关键词： 氧化锌纳米管 电子结构 共掺杂 第一性原理计算     

电化学法制备高密度导电聚吡咯的性能研究

系统地研究了溶剂、温度和聚合电流密度对电化学制备本征导电聚吡咯 (PPy)膜密度的影响,分别用四探针法和热失重(TG)法研究了不同密度的PPy膜的电导率和热稳定性.用循环伏安法(CV)和电化学阻抗谱(EIS)法比较了不同密度的PPy膜的电化学性能.研究表明,在室温下,在乙氰/水(AN/H₂O, 99/1)溶液比在水溶液中容易得到高密度的PPy膜.高聚合电流密度(如10mA/cm²)可以进一步提高PPy膜的密度,用X射线光电子能谱(XPS)对其结构进行了分析.在AN/H₂O(99/1)溶液中用小电流密度(0.1mA/cm²)聚合时,低温(-20℃)有利于提高PPy膜的密度;然而在高电流密度(10mA/cm²)时, 低温(-20℃)不利于提高PPy膜的密度.高密度的PPy膜(1.42g/cm³)用电流密度10mA/cm²在0℃的AN/H₂O(99/1)溶液中制得.该合成方法和常用的低温低电流密度方法制备高密度的PPy膜相比, 合成时间短,条件易实现,更利于实用化.更重要的是,高密度的PPy膜不仅具有高电导率(～220S/cm)和高热稳定性,还具有低的电化学活性.因此,高密度的PPy膜不仅是一种优异的电子导电的电极材料,而且是一种潜在的优异的防腐材料. 关键词： 聚吡咯膜 密度 电导率 热稳定性     

CO_2活化温度对N-C复合碳气凝胶结构及电化学性能的影响

采用CO2活化工艺对氮掺杂碳气凝胶(N-CA)的结构进行重整,并系统研究了活化温度对活化氮掺杂碳气凝胶(N-ACA)孔结构及电化学性能的影响。利用N2吸附数据、X-光电子能谱(XPS)和元素分析对样品的结构及元素组成进行表征。结果表明,随活化温度的升高,N-ACA的比表面积逐渐增大,其含有的氮原子分数逐渐减少,吡咯氮含量明显增加。利用循环伏安(CV)、电化学阻抗谱(EIS)等测试技术评价了碳气凝胶样品在6mol·L-1 KOH电解液中的电化学性能,结果发现,合理的孔结构与较高的吡咯氮含量是影响电容器比容量的关键因素。在5mV·s-1扫描速率下测试950-N-ACA电极的比电容值高达267.4F·g-1,经1000次充放电后比电容损失值在1.5%以内。     

镱铝共掺石英玻璃的制备及其发光特性的研究

提出了一种新的溶液掺杂与非化学气相沉积(non-chemical vapor deposition, NCVD)熔融相结合的方法制备稀土掺杂石英基玻璃,并采用该方法制备出组分为98SiO₂-0.5Yb₂O₃-1.5Al₂O₃wt%、折射率n_D =1.519和密度 ρ=2.62 g/cm³的镱铝共掺石英玻璃.经实验测试表明:它的 关键词： 镱铝共掺石英玻璃 溶液掺杂 发光特性 光子晶体光纤     

基于氮掺杂碳量子点/DNA自组装纳米探针检测鱼精蛋白

将柠檬酸置于单乙醇胺中,通过简单加热实现快速、大规模的合成氮掺杂荧光碳点。所得氮掺杂碳量子点被370 nm 的光激发后在458 nm 处有较强的荧光发射,最大吸收波长为365.085 nm。脱氧核糖核苷酸能增强该碳量子点的荧光且具有相关线性关系,因而制备了氮掺杂碳点与脱氧核糖核苷酸的杂交纳米复合物（纳米探针）,并首次用于检测鱼精蛋白。在实验条件最佳情况下,该方法简便、选择性好,该分析方法的线性检测范围为1~10 μg·mL^-1,检出限可达0.61 μg·mL^-1。     

Sm~(3+),Sr~(2+)共掺杂对CeO_2基电解质性能影响的密度泛函理论+U计算

Sm~(3+),Sr~(2+)共掺杂CeO_2的离子电导率被证实可高达Sm~(3+)掺杂CeO_2离子电导率的近两倍,然而,共掺杂对CeO_2电导率的作用机理尚不明确.本文利用第一性原理计算的密度泛函理论+U方法,对Sm~(3+)和Sr~(2+)共掺杂的CeO_2进行了系统的研究,对比Sm~(3+)或Sr~(2+)单掺杂的CeO_2体系,计算并分析了共掺杂体系的电子态密度、能带结构、氧空位形成能以及氧空位迁移能等微观属性.计算结果表明,Sm~(3+),Sr~(2+)的共掺杂对CeO_2基电解质性能的提高具有协同效应,二者的共掺杂不仅能协同抑制CeO_2体系的电子电导率,还能在单掺杂CeO_2的基础上进一步降低氧空位形成能,Sm~(3+)的存在还有助于降低Sr~(2+)对氧空位的俘获作用,而Sr~(2+)的加入则能够在Sm~(3+)掺杂CeO_2的基础上进一步降低最低氧空位迁移能,爬坡式弹性能带方法计算表明共掺杂体系的氧空位迁移能最低可达0.314/0.295 eV,低于Sm~(3+)掺杂CeO_2的最低氧空位迁移能.研究揭示了Sm~(3+),Sr~(2+)共掺杂对CeO_2电导率的协同作用机理,对进一步研发其他高性能的共掺杂电解质材料具有重要的指导意义.     

溶剂热制备锂电池负极材料CNT-ZnFe2O4及其电化学性能

为了改善锂离子电池负极材料ZnFe₂O₄导电性差和循环寿命低的缺点,利用溶剂热反应方法制备了ZnFe₂O₄,并通过复合碳纳米管对ZnFe₂O₄进行改性。充放电测试结果表明：经过50次充放电后,碳纳米管复合改性后的ZnFe₂O₄容量保持在860 mA·h·g^-1,具有较好的循环稳定性。碳纳米管具有良好的导电性与导热性,改善了ZnFe₂O₄导电性差的缺点。     

Synthesis and elevated temperature performance of a polypyrrole-sulfur-multi-walled carbon nanotube composite cathode for lithium sulfur batteries

A sulfur-multi-walled carbon nanotube composite (S/MWCNT) was prepared using a two-step procedure of liquid-phase infiltration and melt diffusion. Polypyrrole (PPy) conductive polymer was coated on the surface of the as-prepared S/MWCNT composite by in situ polymerization of pyrrole monomer to obtain PPy/S/MWCNT composite. The composite materials were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The electrochemical performance of the as-prepared cathode material was investigated at 25, 40, and 70 °C at various rates. It was found that temperature has dual effects on the performance of Li/S cells. Increasing the temperature, on one hand, facilitates the lithium ion transport through the cathode and, on the other hand, leads to faster dissolution of active material into the electrolyte. The PPy coating can effectively trap polysulfides in its porous structure, even at elevated temperatures, leading to the improvement of the discharge capacity, the cycle stability, and the coulombic efficiency. The electrochemical impedance spectroscopy (EIS) results reveal that the PPy coating reduces the formation of passive layer on the cathode surface, even at high temperatures, resulting in a better elevated temperature performance. A high reversible capacity of 945 mAh g^?1 was maintained after 50 cycles for the PPy/S/MWCNT composite at 70 °C at a rate of 0.5 C.     

Facile fabrication of highly flexible,porous PEDOT: PSS/SWCNTs films for thermoelectric applications

High-performance organic composite thermoelectric(TE)materials are considered as a promising alternative for harvesting heat energy.Herein,composite films of poly(3,4-ethyienedioxythiophene):poly(styrene sulfonate)/single-walled carbon nanotubes(PEDOT:PSS/SWCNTs)were fabricated by utilizing a convenient solution mixing method.Thereafter,the as-prepared hybrid films were treated using sulfuric acid(H₂SO₄)to further optimize the TE performance.Film morphological studies revealed that the sulfuric acid treated PEDOT:PSS/SWCNTs composite samples all possessed porous structures.Due to the successful fabrication of highly conductive networks,the porous nano-architecture also exhibited much more excellent TE properties when compared with the dense structure of the pristine samples.For the post-treated sample,a high power factor of 156.43μW·m^-1·K^-2can be achieved by adjusting the content of CNTs,which is approximately 3 orders of magnitude higher than that of the corresponding untreated samples(0.23μW·m^-1·K^-2).Besides,the obtained films also showed excellent mechanical flexibility,owing to the porous nanostructure and the strong p–p interactions between the two components.This work indicates that the H₂SO₄ treatment could be a promising strategy for fabricating highly-flexible and porous PEDOT:PSS/SWCNTs films with high TE performances.     

Activated carbon aerogel as electrode material for coin-type EDLC cell in organic electrolyte

Carbon aerogel (CA) was prepared by a carbonization of resorcinol–formaldehyde (RF) polymer gels, and it was chemically activated with KOH to obtain activated carbon aerogel (ACA) for electrode material for EDLC in organic electrolyte. Coin-type EDLC cells with two symmetrical carbon electrode were assembled using the prepared carbon materials. Electrochemical performance of the carbon electrodes was measured by galvanostatic charge/discharge and cyclic voltammetry methods. Activated carbon aerogel (20.9 F/g) showed much higher specific capacitance than carbon aerogel (7.9 F/g) and commercial activated carbon (8.5 F/g) at a scan rate of 100 mV/s. This indicates that chemical activation with KOH served as an efficient method to improve electrochemical performance of carbon aerogel for EDLC electrode in organic electrolyte. The enhanced electrochemical performance of activated carbon aerogel was attributed to the high effective surface area and the well-developed pore structure with appropriate pore size obtained from activation with KOH.     

Lithium ion batteries cathode material: V2O5

Among all the known electrode materials, vanadium pentoxide (V₂O₅) has high reversible capacity. It is a very valuable material for research of the complexity, rich structure and morphology. However, it also has some disadvantages, such as poor cycle stability, low discharge voltage, low conductivity and Li⁺ diffusion coefficient. In this regard, researchers have carried out a lot of research, such as using various methods to improve the nanostructures, introducing heterostructures, introducing point defects or cation doping in the crystal structure, etc. The electrochemical performance of V₂O₅ has been significantly improved in reversible capacity, high-rate capacity and long-term cycle stability. In this paper, V₂O₅ based nanostructure with different chemical composition are briefly introduced, and it covers V₂O₅ nanomaterials with different morphology, including 1D nanorods, nanobelts, nanotubes, 2D leaf like nanosheets and other nanosheets, and 3D hollow structures, porous nanostructures, porous eggshell microsphere structures. The composite nanomaterials of V₂O₅ and different carbonaceous supports are also introduced. Finally, the V₂O₅ composite materials doped with cations are discussed. The electrochemical performance of V₂O₅ based electrode can be improved effectively by obtaining appropriate nanostructure and optimized chemical composition.     

Growth of aligned carbon nanotube arrays on metallic substrate and its application to supercapacitors

Aligned carbon nanotube arrays (ACNTAs) with lengths up to 150 μm were fabricated on metallic alloy (Inconel 600) substrates by pyrolysis of iron (II) phthalocyanine (FePc) in the presence of ethylene (C₂H₄). The as-grown ACNTAs, formed by aligned multi-walled carbon nanotubes with high purity, were characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and Raman spectroscopy techniques. The ACNTAs were used directly as electrode materials in supercapacitors with (Et)₄NBF₄ + propylene carbonate (PC) as electrolyte, and their electrochemical properties were investigated. A rectangular-shaped cyclic voltammetry (CV) curve was observed even at a sweep rate of 1000 mV s⁻¹. The specific capacitance measured at 1000 mV s⁻¹ was about 57 % (47 F g⁻¹) of that obtained at 1 mV s⁻¹ (83 F g⁻¹), and an equivalent series resistance (ESR) of 0.55 Ω was measured for the ACNTA and activated carbon pair electrodes embedded in a coin cell. The results indicated that the ACNTAs could be a promising candidate as electrode materials in supercapacitors.     

Synthesis and electrochemical performance of hole-rich Li4Ti5O12 anode material for lithium-ion secondary batteries

Hole-rich Li₄Ti₅O₁₂ composites are synthesized by spray drying using carbon nanotubes as additives in precursor solution, subsequently followed calcinated at high temperature in air. The structure, morphology, and texture of the as-prepared composites are characterized with XRD, Raman, BET and SEM techniques. The electrochemical properties of the as-prepared composites are investigated systematically by charge/discharge testing, cyclic voltammograms and AC impedance spectroscopy, respectively. In comparison with the pristine Li₄Ti₅O₁₂, the hole-rich Li₄Ti₅O₁₂ induced by carbon nanotubes exhibits superior electrochemical performance, especially at high rates. The obtained excellent electrochemical performances of should be attributed to the hole-rich structure of the materials, which offers more connection-area with the electrolyte, shorter diffusion-path length as well faster migration rate for both Li ions and electrons during the charge/discharge process.     

Cu,Fe掺杂LiNbO_3晶体电子结构和光学性质的第一性原理研究

利用基于密度泛函理论的第一性原理对Cu,Fe单掺及共掺LiNbO_3晶体的电子结构和光学性质进行了计算.结果显示:Cu,Fe单掺杂LiNbO_3晶体禁带内均产生了杂质能级,主要由Cu3d,Fe3d轨道及O 2p轨道贡献;共掺LiNbO_3晶体禁带内出现了双能级结构,深能级由Cu3d和O2p轨道贡献,浅能级由Fe3d和O2p轨道贡献.Cu,Fe单掺和共掺LiNbO_3晶体带隙依次缩小,在可见光区的光吸收明显增强.共掺LiNbO_3在445和630nm左右分别表现出一个宽吸收峰,比单掺LiNbO_3晶体表现出更好的光吸收性质.研究表明,Fe占Nb位比Fe占Li位的双掺样品在双光存储应用中更有优势;同时,浓度比[Fe2+]/[Fe3+]值的适当降低有助于这种优势的形成.     

Emission properties of Ta-centres in KCl

Electrolytic colouration at about 600°C and 350 V/cm, for KCl crystal containing Pb²⁺ and for KCl:Pb²⁺ crystals co-doped with Li⁺, Na⁺ and Rb⁺ has been undertaken. Several absorption bands were observed in both doped and co-doped crystals in the visible-UV region. Excitation into these bands gives rise to the same 0.86 eV emission band except for the Li⁺-co-doped crystal which gives rise to a 0.80 eV emission band. These absorption bands are due to the same T_a-centre related to Pb⁻. The observed infrared emission intensity of the crystal with F-centres is higher than of without F-centres.