Rational Design of Carbon Nanomaterials for Electrochemical Sodium Storage and Capture

Electrochemical sodium storage and capture are considered an attractive technology owing to the natural abundance, low cost, safety, and cleanness of sodium, and the higher efficiency of the electrochemical system compared to fossil‐fuel‐based counterparts. Considering that the sodium‐ion chemistry often largely deviates from the lithium‐based one despite the physical and chemical similarities, the architecture and chemical structure of electrode materials should be designed for highly efficient sodium storage and capture technologies. Here, the rational design in the structure and chemistry of carbon materials for sodium‐ion batteries (SIBs), sodium‐ion capacitors (SICs), and capacitive deionization (CDI) applications is comprehensively reviewed. Types and features of carbon materials are classified into ordered and disordered carbons as well as nanodimensional and nanoporous carbons, covering the effect of synthesis parameters on the carbon structure and chemistry. The sodium storage mechanism and performance of these carbon materials are correlated with the key structural/chemical factors, including the interlayer spacing, crystallite size, porous characteristics, micro/nanostructure, morphology, surface chemistry, heteroatom incorporation, and hybridization. Finally, perspectives on current impediment and future research directions into the development of practical SIBs, SICs, and CDI are also provided.     

超级电容器电极用N-掺杂多孔碳材料的研究进展

多孔碳材料作为双电层电容器的主要电极材料,已成功应用于商业化超级电容器。但作为电极材料,纯碳材料表面疏水、内阻较大、电容较低等缺点使其进一步发展受到制约。近年来,随着超级电容器的迅速发展,氮掺杂多孔碳材料作为其电极材料引起研究人员的广泛关注,并采用不同的制备方法成功合成了一系列结构不同、性能优异的氮掺杂碳材料。基于超级电容器氮掺杂多孔碳电极材料的最新研究进展,首先介绍了氮在碳材料中的基本存在形式及对碳电极材料性能的影响,然后重点评述了氮掺杂碳电极材料的制备,最后总结了超级电容器氮掺杂碳材料的发展趋势。     

竹基多孔炭上生长一维纳米炭

采用CVD法,以二甲苯为炭源,二茂铁、氯化铁等为催化剂在竹基多孔炭上生长一维纳米炭。采用扫描电镜、透射电镜及氮吸附仪等对一维纳米炭/竹基多孔炭的形貌、微结构与比表面积进行了表征。结果表明:采用CVD法可以在不同比表面积的竹基多孔炭上生长一维纳米炭(包括炭纳米管和炭纳米纤维),竹基多孔炭的比表面积越高,所获得的一维纳米炭/竹基多孔炭复合物的比表面积越大。     

Carbon materials for chemical capacitive energy storage

Carbon materials have attracted intense interests as electrode materials for electrochemical capacitors, because of their high surface area, electrical conductivity, chemical stability and low cost. Activated carbons produced by different activation processes from various precursors are the most widely used electrodes. Recently, with the rapid growth of nanotechnology, nanostructured electrode materials, such as carbon nanotubes and template-synthesized porous carbons have been developed. Their unique electrical properties and well controlled pore sizes and structures facilitate fast ion and electron transportation. In order to further improve the power and energy densities of the capacitors, carbon-based composites combining electrical double layer capacitors (EDLC)-capacitance and pseudo-capacitance have been explored. They show not only enhanced capacitance, but as well good cyclability. In this review, recent progresses on carbon-based electrode materials are summarized, including activated carbons, carbon nanotubes, and template-synthesized porous carbons, in particular mesoporous carbons. Their advantages and disadvantages as electrochemical capacitors are discussed. At the end of this review, the future trends of electrochemical capacitors with high energy and power are proposed.     

Preparation and CO_2 adsorption properties of porous carbon by hydrothermal carbonization of tree leaves

Porous carbon materials were prepared by hydrothermal carbonization(HTC) and KOH activation of camphor leaves and camellia leaves. The morphology, pore structure, chemical properties and CO_2 capture ability of the porous carbon prepared from the two leaves were compared. The effect of HTC temperature on the structure and CO_2 adsorption properties was especially investigated. It was found that HTC temperature had a major effect on the structure of the product and the ability to capture CO_2. The porous carbon materials prepared from camellia leaves at the HTC temperature of 240℃ had the highest proportion of microporous structure, the largest specific surface area(up to 1823.77 m~2/g) and the maximum CO_2 adsorption capacity of 8.30 mmol/g at 25℃ under 0.4 MPa. For all prepared porous carbons, simulation results of isothermal adsorption model showed that Langmuir isotherm model described the adsorption equilibrium data better than Freundlich isotherm model. For porous carbons prepared from camphor leaves, pseudo-first order kinetic model was well fitted with the experimental data. However,for porous carbons prepared from camellia leaves, both pseudo-first and pseudo-second order kinetics model adsorption behaviors were present. The porous carbon materials prepared from tree leaves provided a feasible option for CO_2 capture with low cost, environmental friendship and high capture capability.     

Porous carbons

Carbon in dense as well as porous solid form is used in a variety of applications. Activated porous carbons are made through pyrolysis and activation of carbonaceous natural as well as synthetic precursors. Pyrolysed woods replicate the structure of original wood but as such possess very low surface areas and poor adsorption capacities. On activation, these exhibit increased adsorption volumes of 0.5-0.8 cm³/gm and surface areas of 700–1800 m²/gm depending on activation conditions, whether physical or chemical. Former carbons possess mixed pore size distribution while chemically activated carbons predominantly possess micropores. Thus, these carbons can be used for adsorption of wide distributions of molecules from gas to liquid. The molecular adsorption within the pores is due to single layer or multilayer molecule deposition at the pore walls and hence results in different types of adsorption isotherm. On the other hand, activated carbon fibres with controlled microporous structure and surface area in the range of 2500 m²/gm can be developed by controlled pyrolysis and physical activation of amorphous carbon fibres. Active carbon fibres with unmatchable pore structure and surface characteristics are present and futuristic porous materials for a number of applications from pollution control to energy storage.     

熔盐法制备氮掺杂多孔炭及其催化脱硫性能

采用熔融盐合成技术, 以生物质葡萄糖和富氮三聚氰胺为前驱体, 成功制备得到具有发达孔隙结构(BET表面积: 1355 m²/g)和极高氮掺杂量(20.73wt%)的氮掺杂多孔炭材料。X射线光电子能谱(XPS)分析表明, 多孔炭材料中的氮原子主要以吡咯及吡啶构型存在, 这两种形态的氮原子有利于硫化氢的吸附及催化氧化。在常温、常压下, 所制备氮掺杂多孔炭对硫化氢非金属催化转化为单质硫的脱除硫容高达1.10 g/g。该合成方法简便易行, 有望实现氮掺杂多孔炭材料的批量和廉价制备, 合成的氮掺杂多孔炭在污染物控制领域应用潜能巨大。     

基于煤萃取物的类石墨状多孔炭的制备及其电容性能研究

以褐煤萃取物为炭前驱体, MgO为阻隔剂, KOH为活化剂, 在800℃惰性气氛下制备出类石墨状多孔炭材料。对该多孔炭材料进行了红外(FTIR)、X射线衍射(XRD)、透射电镜(TEM)和拉曼(Raman)表征。以活化前和活化后多孔炭为电极材料, 利用循环伏安、恒电流充放电、交流阻抗对其进行了电化学电容性能评价和比较。结果表明: 活化后炭材料呈现多孔的薄膜状, 比表面积高达1396 m²/g, 而活化前炭材料比表面积仅为138.4 m²/g。当电流密度为1 A/g和4 A/g时, 活化后炭材料比电容分别为533 F/g和390 F/g; 而活化前炭材料对应的比电容为366 F/g和198 F/g。在电流密度为5 A/g下循环8000圈后, 活化前后炭材料的电容保持率分别为72.5%和89.6%。可见, 经过KOH活化后的炭材料比电容和电化学稳定性有了显著提高。该研究证明阻隔剂和活化剂的使用, 能够获得高度柔性的高电容性能的类石墨状多孔炭。     

Transforming Hair into Heteroatom‐Doped Carbon with High Surface Area

Herein, a unique approach to dispose of human hair by pyrolizing it in a regulated environment is presented, yielding highly porous, conductive hair carbons with heteroatoms and high surface area. α‐keratin in the protein network of hair serves as a precursor for the heteroatoms and carbon. The carbon framework is ingrained with heteroatoms such as nitrogen and sulfur, which otherwise are incorporated externally through energy‐intensive, hazardous, chemical reactions using proper organic precursors. This judicious transformation of organic‐rich waste not only addresses the disposal issue, but also generates valuable functional carbon materials from the discard. This unique synthesis strategy involving moderate activation and further graphitization enhances the electrical conductivity, while still maintaining the precious heteroatoms. The effect of temperature on the structural and functional properties is studied, and all the as‐obtained carbons are applied as metal‐free catalysts for the oxygen reduction reaction (ORR). Carbon graphitized at 900 °C emerges as a superior ORR electrocatalyst with excellent electrocatalytic performance, high selectivity, and long durability, demonstrating that hair carbon can be a promising alternative for costly Pt‐based electrocatalysts in fuel cells. The ORR performance can be discussed in terms of heteroatom doping, surface properties, and electrical conductivity of the resulting porous hair carbon materials.     

酚醛树脂聚合相分离热解制备介孔碳

采用酚醛树脂聚合相分离热解制备多孔碳, 用压汞仪和场发射扫描电镜对多孔碳性能进行表征, 同时研究了固化催化剂含量对多孔碳性能的影响. 实验结果表明, 制备得到的多孔碳的孔呈交联互通状且孔径分布较窄, 大部分孔分布在20～50nm之间. 多孔碳的平均孔径约40nm. 高固化催化剂含量使多孔碳具有更薄的孔壁及更高的显气孔率. 当固化催化剂含量为15%时, 多孔碳的显气孔率为54.3%. 胶凝速度以及体积收缩是改变多孔碳性能的两个因素.     

“Cubism” on the Nanoscale: From Squaric Acid to Porous Carbon Cubes

3D cube‐shaped composites and carbon microparticles with hierarchically porous structure are prepared by a facile template‐free synthesis route. Via the coordination of zinc acetate dihydrate and squaric acid, porous 3D cubic crystalline particles of zinc squarate can be obtained. These are easily transformed into the respective zinc oxide carbon composites under preservation of the macromorphology by heat treatment. Washing of the composite materials results in hierarchically porous carbons with high surface areas (1295 m² g^–1) and large pore volumes (1.5 cm³ g^?1) under full retention of the cube‐like architecture of the initial crystals. The materials are shown to be promising electrode materials for supercapacitor applications with a specific capacitance of 133 F g^?1 in H₂SO₄ at a scan rate of 5 mV s^?1, while 67% of this specific capacitance is retained, when increasing the scan rate to 200 mV s^?1.     

以石油渣油为原料制备多孔炭

以石油渣油为原料,分别采取传统的水蒸气活化和类模板法制备多孔炭材料,并采用氮吸附、XRD和SEM等分析手段对得到的多孔炭进行了表征。结果表明,水蒸气活化制备的多孔炭以微孔为主,且随着活化时间的增加,比表面积增大,炭收率减小。而类模板法制备的多孔炭以中孔为主,且随着MgO/渣油配比值的增加,其比表面积随之增大,炭收率变化不大。     

NaY分子筛模板法合成多孔炭材料

采用NaY沸石分子筛作模板,乙酰丙酮为炭前驱体,使用液相浸渍-气相沉积工艺合成了富含微孔和中孔结构的多孔炭材料并对其进行了表征.所合成的多孔炭比表面积1351m2/g,孔容0.892cm3/g,微孔率0.63,孔径分布多在0.8nm～3.0nm之间.     

Recent Progress in the Synthesis of Porous Carbon Materials

In this review, the progress made in the last ten years concerning the synthesis of porous carbon materials is summarized. Porous carbon materials with various pore sizes and pore structures have been synthesized using several different routes. Microporous activated carbons have been synthesized through the activation process. Ordered microporous carbon materials have been synthesized using zeolites as templates. Mesoporous carbons with a disordered pore structure have been synthesized using various methods, including catalytic activation using metal species, carbonization of polymer/polymer blends, carbonization of organic aerogels, and template synthesis using silica nanoparticles. Ordered mesoporous carbons with various pore structures have been synthesized using mesoporous silica materials such as MCM‐48, HMS, SBA‐15, MCF, and MSU‐X as templates. Ordered mesoporous carbons with graphitic pore walls have been synthesized using soft‐carbon sources that can be converted to highly ordered graphite at high temperature. Hierarchically ordered mesoporous carbon materials have been synthesized using various designed silica templates. Some of these mesoporous carbon materials have successfully been used as adsorbents for bulky pollutants, as electrodes for supercapacitors and fuel cells, and as hosts for enzyme immobilization. Ordered macroporous carbon materials have been synthesized using colloidal crystals as templates. One‐dimensional carbon nanostructured materials have been fabricated using anodic aluminum oxide (AAO) as a template.     

Performance of electrical double layer capacitors with porous carbons derived from rice husk

The porous structure and electrochemical double layer capacitance of porous carbons prepared from rice husks by using alkali hydroxide as activating agents were investigated. Three samples of carbons prepared by NaOH-activation, three samples prepared by KOH-activation and two samples of commercial carbons have been studied. The porosity of the carbons was characterized by nitrogen adsorption isotherms at 77 K and electrochemical constant current cycling method was used to measure the double layer capacitance. The specific capacitance of the carbons is not linearly proportional to the surface area. Additionally, the double layer capacitance strongly depends on the pore structure and the functional groups. A specific capacitance larger than 200 F g⁻¹ was achieved by using the porous carbon prepared with NaOH (activation temperature: 750 °C; activation time: 30 min). All the carbons prepared with rice husk in this study have larger double layer capacitance (125–210 F g⁻¹) than the commercial grade carbons (78–100 F g⁻¹).     

过渡金属/活性炭电极的电容性能研究

选用微孔和中孔活性炭采用浸渍法负载金属离子,考察在水性电解质中用于超级电容器的活性炭复合电极的电化学性能,探讨活性炭在负载前后的放电容量变化情况.采用低温氮吸附和直流恒流循环实验考察活性炭复合电极的孔结构及电容性能.研究表明:金属Cu、Mn具有比较明显的准电容效应,Co、Ni可提高中孔活性炭的放电容量,而金属Mo、Fe和Y的准电容效应不显著;中孔活性炭负载金属的作用明显强于微孔活性炭;中孔活性炭负载金属Cu时,放电容量随负载量的增加而上升.     

Green Synthesis of Hierarchically Porous Carbon Nanotubes as Advanced Materials for High‐Efficient Energy Storage

Hierarchically porous carbon nanomaterials with well‐defined architecture can afford a promising platform for effectively addressing energy and environmental concerns. Herein, a totally green and straightforward synthesis strategy for the fabrication of hierarchically porous carbon nanotubes (HPCNTs) by a simple carbonization treatment without any assistance of soft/hard templates and activation procedures is demonstrated. A high specific surface area of 1419 m² g^?1 and hierarchical micro‐/meso‐/macroporosity can be achieved for the HPCNTs. The unique porous architecture enables the HPCNTs serving as excellent electrode/host materials for high‐performance supercapacitors and Li–sulfur batteries. The design strategy may pave a new avenue for the rational synthesis of hierarchically porous carbon nanostructures for high‐efficient energy storage applications.     

Performance of Electric Double Layer Capacitors using Active Carbons Prepared from Petroleum Coke by KOH and Vapor Re-Etching

The electrochemical storage of energy in a special kind of active carbon materials used as capacitor electrodes is considered. Petroleum coke was used for preparation of carbons with different porosities by KOH and vapor etching with catalysis of FeCl3 in turn. Carbon electrodes were fabricated and used as electrodes of double layer capacitors.Nitrogen adsorption was used to characterize the porous structure of the carbons. The electrochemical performance of the capacitors in 6mol/L KOH was investigated with constant current charge and discharge experiments. A specific capacitance larger than 160F/g was achieved with an electrode composed of 75% active carbon with a specific surface area of 1180m^2/g and 20% graphite as conductive agent. Evaluation of capacitor performance was conducted by different techniques, e.g. voltammetry and impedance spectroscopy. Characteristics of the capacitor were also discussed. A hybrid power source consisting of nickel-hydrogen and double layer capacitor was demonstrated by powering successfully a simulated power load encountered in communication equipment.     

Fabrication of 3D carbon nanotube/porous carbon hybrid materials

Three dimensional hybrid carbon materials have been prepared using different biomass-derived porous carbons as catalyst supports for growing multi-walled carbon nanotubes (MWCNTs) via a chemical vapor deposition method. The nickel catalyst-loaded supports before and after growing MWCNTs were characterized by scanning and transmission electron microscopy, Fourier transform infrared spectroscopy spectra, and mercury porosimetry. The results show that the grown MWCNTs microstructures are closely related to the porous structures and surface conditions of the carbon supports. By using bamboo as template, a porous carbon support with a large total pore volume, appropriate pore size, and abundant favorable surface functional groups is obtained, which is found to be an ideal support for growing the MWCNTs. Investigation of growth mechanism demonstrated that the combination of appropriate porous structures and surface conditions plays an essential role in catalyst distribution and MWCNTs growth.     

磁性多孔碳材料的研究进展

磁性多孔碳材料同时具有磁性和多孔性质,其拥有丰富的孔道结构、高的比表面积、高孔容、良好的活性位点和磁性可分离等优异的性能,可以很好的解决多孔碳材料在应用过程中难分离回收等问题,因此,磁性多孔碳材料已经在吸附领域得到广泛的应用.按照孔径大小、磁性强弱以及组合方式的不同将磁性多孔碳材料进行了分类,并综述了近年来磁性多孔碳材...