百香果皮基原位氮掺杂多孔碳/硫复合正极的制备及储锂性能

以生物质百香果皮为碳源,KHCO3为活化剂,采用同步活化碳化方法制备原位氮掺杂的分级多孔碳材料,将其与单质硫复合制得多孔碳/硫正极材料。通过X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等表征技术对制备材料的物相组成、微观形貌、比表面积及孔结构进行研究分析。同时,利用紫外可见吸收光谱研究了多孔碳对多硫化物的吸附作用,用恒电流充放电测试了不同硫含量(60%～80%)的多孔碳/硫复合正极材料的电化学性能。结果表明,制得的多孔碳材料为无定型,具有1 093 m²·g^-1的高比表面积和0.63 cm³·g^-1的孔容;丰富的多孔结构和原位氮掺杂对多硫化物的物理化学协同吸附作用,有效降低了锂硫电池的“穿梭效应”,提高了电池的放电比容量和循环性能。硫含量为60%的多孔碳/硫复合材料,在0.05C和0.2C倍率下可释放1 057.7和763.4 mAh·g^-1的高初始放电比容量,在1C的高倍率下循环300次后的保持率为75%。     

碳化硅衍生碳/球形天然石墨复合材料的制备及其结构调控

为满足储能领域对于材料兼具高能量密度和高功率密度的需求, 本文旨在将具有特殊孔隙结构的碳化物衍生碳与具有高导电性和高能量存储密度的石墨化碳(球形天然石墨)相复合, 制备得到一种多孔碳化硅衍生碳/球形天然石墨(SiC-CDCs@NG)复合材料. 采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、拉曼光谱、N₂吸/脱附等方法对材料的组成、结构、形貌、孔结构和比表面积等进行了表征. 结果表明,SiC-CDCs@NG材料具有较大的且可调节的比表面积和微孔体积, 微孔孔径集中在0.5-0.7 nm范围内; 通过改变NG/Si 摩尔比, 可以有效调控CDCs壳和NG核在复合材料中的组成分布、CDCs微孔的体积、孔径分布和比表面积.     

Preparation and characterization of templated porous carbons from sucrose by one-pot method and application as a CO2 adsorbent

The templated porous carbons were prepared from sucrose by one-pot method. In this method in which the pre-synthesis of the hard template is eliminated, the porous carbons were produced by organic-inorganic self-assembly of sucrose, tetraethyl ortosilicate (TEOS), Pluronic P123 and n-butanol in an acidic medium, and subsequent carbonization. The synthesis parameters such as sucrose amount, TEOS molar ratio and carbonization temperature were evaluated for describing their effects on the pore structures of the synthesized carbons. The prepared porous carbons were characterized by N₂ adsorption, thermogravimetric analysis (TGA), Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) techniques. The carbon dioxide adsorption uptakes of the obtained porous carbons were determined at 1 bar and 273 K. The templated carbon obtained with the lowest TEOS molar ratio exhibited the highest BET surface area of 1289 m²/g and micropore volume of 0.467 cm³/g, and showed the highest CO₂ uptake of 2.28 mmol/g.     

介孔炭的直接制备及其电化学性能研究

以柠檬酸镁为原料,采用直接碳化法制备介孔炭电极材料。N2吸附测试表明,所制备多孔炭的比表面积达2 000 m2·g-1左右,介孔孔容和平均孔径随着炭化温度的升高而增加,当炭化温度大于800℃时,能够制备出以介孔结构为主的多孔炭材料。电化学测试表明,MgC-800和MgC-900具有优异的电化学电容特性。与硬模板法制备的OMC相比,MgC-800和MgC-900在实验电流密度范围内具有更大的比电容值,这应当归功于它们巨大的比表面积以及有利于电解质离子扩散的介孔结构。     

Preparation and characterization of helical carbon/silica nanofibers with lamellar mesopores on the surfaces

Helical 1,2-ethylene-silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like mesopores inside were prepared according to literature procedures. After carbonization, helical carbon/ silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like micropores inside were obtained. The morphologies and pore architectures of the carbon]silica nanofibers were characterized using transmission electron microscopy, field-emission scanning electron microscopy, powder X-ray diffraction and N2 sorptions. Although the mesopores inside shrank into micropores, the helical nanostructure remained. Moreover, several carbon/silica nanofibers with lamellar mesopores on the surfaces and concentric circular micropores inside were also obtained. After being calcined in air, helical silica nanofibers with lamellar mesopores on the surfaces and twisted rod-like micropores inside were produced as well.     

Interconnected nitrogen-doped carbon nanofibers derived from polypyrrole for high-performance Li/S batteries

Interconnected nitrogen-doped carbon nanofibers (INC) prepared through the carbonization of polypyrrole (PPy) precursor is designed as scaffold to load sulfur. The BET measurement showed that INC possessed abundant mesopores with a relatively high specific surface area and a large total pore volume. The sulfur/INC (S/INC) composite was synthesized by a melt-diffusion of sulfur nanoparticle into INC network. Transmission electron microscopy showed the formation of a nanofiber structure with uniform sulfur coating on the surface of INCs. When tested as cathodes for Li/S batteries, a high initial discharge capacity of 1173 mAh g^–1 and a reversible capacity of 702 mAh g^–1 after 50 cycles at 0.1 C are achieved, which ascribe to the chemical and physical adsorption properties of mesoporous and nitrogen-doped INC.     

静电纺丝制备多孔碳纳米纤维及其电化学电容行为

采用静电纺丝技术,以聚丙烯腈(PAN)/醋酸锌为前驱体制备复合纳米纤维,随后经碳化、酸化获得多孔碳纳米纤维.扫描电子显微镜(SEM)观察发现,碳纳米纤维表面分布大量孔洞.N2吸脱附等温曲线(BET)测试材料比表面积达413m2·g-1.循环伏安法(CV)和恒流充放电(CP)性能测试表明:多孔碳纳米纤维具有较好的电化学性能,在1A·g-1的电流密度下比电容达275F·g-1.相比碳纳米纤维比容量提高了162%.     

Highly Porous Amidoximed Carbon Nanofibers Supported Palladium(0) Nanoparticle Catalyzed Heck Reaction

Highly porous amidoximed carbon nanofibers(AOCNFs), which were fabricated via a conventional electrospinning technique followed by chemically modification, impregnation-reduction and carbonization process, had been used for the immobilization of palladium nanoparticles(Pd NPs) catalyst. During the carbonization process, polystyrene(PS) was selectively decomposed from bicomponent fibers, generating porous fibers. Fourier transform infrared spectroscopy(FTIR) result revealed the functional groups on PAN-PS fibers(PAN=polyacrylonitrile), AOPAN-PS fibers and AOCNFs; scanning electron microscopy(SEM) was used to observe the morphology of all stages of nanofibers; transmission electron microscopy(TEM) result gave the structure of through-hole morphology clearly visible and the dispersion of Pd NPs on the surface of nanofibers; and X-ray photoelectron spectra(XPS) confirmed that Pd nanoparticles on the surface of AOCNFs was of the metallic state. Moreover, the as-prepared catalyst exhibited high catalytic activity and efficient recycle for Heck coupling reactions between iodobenzene and acrylates.     

由微孔棒状羟基磷灰石为模板合成的新型层次孔炭材料的电化学电容性能

电化学电容器已经成为极具潜力的可满足高功率需求的储能系统器件. 多孔炭具有大比表面积、高导电性、化学惰性、廉价及可调孔结构等优势, 因此成为电化学电容器最为常用的电极材料. 本文报道由微孔棒状羟基磷灰石为模板及蔗糖为碳源合成的新型具有层次孔道结构的孔炭材料的电化学电容器的性能. 采用X射线衍射分析仪、扫描电子显微镜、透射电子显微镜、X射线光电子能谱及BET表面分析仪表征了合成的多孔炭的形貌及表面特性. 采用循环伏安法、交流阻抗图谱分析及恒流充放电评价多孔炭材料在1 mol·L^-1硫酸中的电化学电容性能. 多孔炭具有高的比表面积(719.7 m²·g^-1)和大的孔容(1.32 cm³·g^-1), 其无序的孔道由任意分布的微孔、坍塌的中孔及类模板形状的相互交织的棒状中孔组成. 随着炭化温度的增加, 微孔及棒状中孔的密度随之降低, 在炭化温度高达900℃时, 孔径分布图上出现了三个峰. 正是由于这些特殊的结构特征, 由900℃炭化得到的多孔炭制成的电极展示出很好的电化学电容性能.     

The study of controlling pore size on electrospun carbon nanofibers for hydrogen adsorption

Polyacrylonitrile (PAN)-based carbon nanofibers (CNFs) were prepared by using electrospinning method and heat treatment to get the media for hydrogen adsorption storage. Potassium hydroxide and zinc chloride activations were conducted to increase specific surface area and pore volume of CNFs. To investigate the relation between pore structure and the capacity of hydrogen adsorption, textural properties of activated CNFs were studied with micropore size distribution, specific surface area, and total pore volume by using BET (Brunauer-Emmett-Teller) surface analyzer apparatus and the capacity of hydrogen adsorption was evaluated by PCT (pressure-composition-temperature) hydrogen adsorption analyzer apparatus with volumetric method. The surface morphology of activated CNFs was observed by SEM (scanning electron microscope) images to investigate the surface change through activation. Even though specific surface area and total pore volume were important factors for increasing the capacity of hydrogen adsorption, the pore volume which has pore width (0.6-0.7 nm) was a much more effective factor than specific surface area and pore volume in PAN-based electrospun activated CNFs.     

Direct carbonization of Al-based porous coordination polymer for synthesis of nanoporous carbon

Nanoporous carbon (NPC) is prepared by direct carbonization of Al-based porous coordination polymers (Al-PCP). By applying the appropriate carbonization temperature, both high surface area and large pore volume are realized for the first time. Our NPC shows much higher porosity than other carbon materials (such as activated carbons and mesoporous carbons). This new type of carbon material exhibits superior sensing capabilities toward toxic aromatic substances.     

Dual template method to prepare hierarchical porous carbon nanofibers for high-power supercapacitors

Hierarchical porous carbon nanofibers serving as electrode materials are prepared through carbonization and hydrofluoric acid treatment of polyacrylonitrile-based electrospinning involving dual templates. The hierarchical porous structures are synergistically tailored by varying template contents in the spinning solution. The carbon nanofibers prepared from the electrospinning of polyacrylonitrile containing 15/15 wt.% polymethylmethacrylate/tetraethyl orthosilicate exhibit the largest specific surface area (699 m² g^?1) and microporous volume (0.196 cm³ g^?1). In 6 M KOH electrolyte, a symmetrical supercapacitor equipped with the hierarchical porous carbon nanofibers demonstrates its high-end specific capacitance of 170 F g^?1, superior rate capability, and high-power density output up to 14.7 kW kg^?1. Cycling evolution indicates capacitance fading is only 5.8 % of initial capacitance at a current density of 1 A g^?1 even after 8,000 cycles. The excellent electrochemical performances of the carbon nanofiber are mainly ascribed to the optimized pore size distributions of both micropores and mesopores and the unique hierarchical pore structures possessed by abundant micropores.     

Hierarchical porous carbon derived from Allium cepa for supercapacitors through direct carbonization method with the assist of calcium acetate

Hierarchical porous carbon was prepared from onion through a direct carbonization method and it was used as suercapacitor electrode material.     

基于聚多巴胺的氮掺杂碳材料的制备及其电化学性能

多孔碳材料由于高的比表面积、优异的电子传导率、良好的化学稳定性等优点在超级电容器电极材料领域被广泛研究。 碳材料的组成及表面孔结构直接影响其电化学性能,为进一步提高碳材料的电容性能,本文首次以聚多巴胺球为前体,KOH为活化剂,通过高温碳化成功制备了良好电化学性能的氮掺杂多孔碳材料。 通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、 X射线粉末衍射(XRD)、傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)和Raman光谱等对所制备的氮掺杂多孔碳材料进行了形貌及结构组成的表征。 在6 mol/L KOH电解液中, 采用循环伏安、恒电流充放电对多孔碳材料的电化学性能进行了研究。 结果表明,由于双电层电容和赝电容的协同作用,在电流密度为1 A/g时,材料的比电容可达269 F/g,充放电循环1000圈后电容仍可保留初始值的93.5%。     

纤维素纳米晶模板法制备多级孔炭材料及其电化学性能

以纤维素纳米晶(CNC)为模板,酚醛树脂为碳源,KOH为活化剂,通过高温碳化制备了多级孔炭材料.采用透射电子显微镜(TEM)、扫描电子显微镜(SEM)和X射线光电子能谱仪(XPS)等手段对合成的一系列炭材料进行了表征.结果表明,前驱体中CNC的降解会形成与CNC直径相当的介孔,KOH活化则会导致炭材料产生大量的微孔和大孔,以及部分4 nm左右较小尺度的介孔,所制备炭材料呈现明显的多级孔特性,其比表面积达554.7 m²/g,总孔体积为0.323 cm³/g.以CNC为模板,KOH活化的炭材料作为电极材料时,在1.0 A/g电流密度下其比电容达202.8 F/g,当电流密度升高至40.0 A/g时,其电容保持率仍达69%,表明该炭材料具有优异的倍率性能;由该电极材料组装的超级电容器在10000次充放电循环后,电容保持率达95%以上,具有良好的循环稳定性.     

KOH活化废弃麻制备活性炭及其结构表征

以日常生活中废弃麻纺品为原料, KOH为活化剂, 采用炭化和活化两步法制备麻质活性炭(LAC). 采用比表面积测定仪在77 K下测定其N2吸附-脱附等温线, 通过Langmuir方程、BET方程和BJH法计算其比表面积、孔体积和孔径分布. 结果表明, 麻质活性炭的BET比表面积为1387.473 m2/g, Langmuir比表面积为1790.573 m2/g, 吸附累积总孔容达0.415 cm3/g; 采用扫描电子显微镜(SEM)、X射线衍射分析仪以及红外光谱仪对麻质活性炭的结构进行了表征, 分析其表面形貌、微观结构及表面化学官能团.     

Preparation of porous carbon directly from hydrothermal carbonization of fructose and phloroglucinol for adsorption of tetracycline

Hydrothermal carbonization of biomass is a promising method to prepare carbonaceous materials. Generally, post physical or chemical activation is necessary to increase surface area and porosity of the carbon. Herein, porous carbonaceous material (FPC) with large surface area (481.7 m²/g) and pore volume (0.73 cm³/g) was prepared directly from hydrothermal carbonization of fructose and phloroglucinol in hydroalcoholic mixture. Structure characteristics of the FPC and its adsorption capacity for a representative antibiotic tetracycline in aqueous solution were investigated. This work provides a green and efficient method to fabricate porous carbonaceous adsorbent that has great potential applications in chemical and environmental fields.     

Carbonization of electrospun poly(acrylonitrile) nanofibers containing multiwalled carbon nanotubes observed by transmission electron microscope with in situ heating

Composite nanofibers with 5% w/w multiwalled carbon nanotubes (MWCNTs) in polyacrylonitrile (PAN) were fabricated using the electrospinning technique. Morphological development during the carbonization process was characterized by transmission electron microscopy (TEM) with in situ heating. It was found that the orientation of graphitic layers increases with temperature and does not change significantly with time during our TEM measurement, except the 750 °C. In the heating stage at 750 °C noticeable enhancement of orientation with time was observed. The presence of embedded CNTs enhances the order of the formed graphitic structures even when the CNTs are irregular or entangled. The results indicate that embedded MWCNTs in the PAN nanofibers nucleate the growth of carbon crystals during PAN carbonization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010     

Synthesis of nitrogen-containing carbon materials for solid polymer fuel cell cathodes

The following nitrogen-containing supports with various nitrogen contents and structure and texture properties were synthesized: carbon nanofibers (N-CNFs) and amorphous microporous carbon materials (N-AMCMs). It was found that the above characteristics can be regulated by varying synthesis conditions: precursor compositions and reaction temperature and time. Mesoporous nitrogen-containing CNFs with a specific surface area of 30–350 m²/g and a pore volume of 0.10–0.83 cm³/g were formed by the catalytic decomposition of a mixture of ethylene with ammonia at 450–675°C. Microporous materials (N-AMCMs) with a specific surface area of 472–3436 m²/g and a micropore volume of 0.22–1.88 cm³/g were prepared by the carbonization of nitrogen-containing organic compounds at 700–900°C. An increase in the carbonization temperature and reaction time resulted in an increase in the specific surface area and microporosity of N-AMCMs, whereas lower temperatures of 450–550°C and reaction times of 1–3 h were optimal for the preparation of N-CNFs with a developed texture. It was found that milder synthesis conditions and higher nitrogen contents of precursors were required for obtaining high nitrogen concentrations in both N-CNFs and N-AMCMs. The synthetic method developed allowed us to prepare carbon supports with nitrogen contents to 8 wt %.     

Nanoporous structured submicrometer carbon fibers prepared via solution electrospinning of polymer blends

A facile means for obtaining submicrometer carbon fibers with a nanoporous structure is presented. A mixture of polyacrylonitrile (PAN) and a copolymer of acrylonitrile and methyl methacrylate (poly(AN-co-MMA)) in dimethylformamide was electrospun into submicrometer fibers with a microphase-separated structure. During the followed oxidation process, the copolymer domains were pyrolyzed, resulting in a nanoporous structure that was preserved after carbonization. The microphase-separated structure of the PAN/poly(AN-co-MMA) electrospun fibers, the morphology, and porous structure of both the oxidized and the carbonized fibers were observed with scanning electron microscopy and transmission electron microscopy. The carbon fibers have diameters ranging from several hundred nanometers to about 1 microm. The nanopores or nanoslits throughout the fiber surface and interior with diameters of several tens of nanometers are interconnected and oriented along the longitudinal axis of the fibers. This unique nanoporous morphology similar to the microphase-separated structure in the PAN/poly(AN-co-MMA) fibers is attributed to the rapid phase separation, solidification, as well as the stretching of the fibers during electrospinning. The pore volume and pore size distribution of the carbonized fibers were investigated by nitrogen adsorption and desorption.