Preparation and electrochemical characterization of activated carbons by chemical-physical activation

A process was proposed based on the combination of chemical and physical activation for the production of activated carbons used as the electrode material for electric double layer capacitor (EDLC). By material characterization and electrochemical methods, the influences of the activitation process on the specific surface area, pore structure and electrochemical properties of the activated carbons were investigated. The results show that specific surface area, the mesopore volume, and the specific capacitance increase with the increase of the mass ratio of KOH to char (m(KOH)/m(char)) and the activation time, respectively. When m(KOH)/m(char) is 4.0, the specific surface area and the mesopore volume reach the maximum values, i.e. 1 960 m²/g and 0.308 4 cm³/g, and the specific capacitance is 120.7 F/g synchronously. Compared with the chemical activation, the activated carbons prepared by chemical-physical activation show a larger mesopore volume, a higher ratio of mesopore and a larger specific capacitance. Foundation item: Project(2007BAE12B01) supported by the National Key Technology Research and Development Program of China     

Influence of KOH activation techniques on pore structure and electrochemical property of carbon electrode materials

1 INTRODUCTIONSupercapacitor is a kind of newenergy storagedevice , which can fill the gap between the conven-tional capacitor and the battery[1 ,2]. Supercapa-ciors are nowutilizedin many fields ,such as spaceindustry ,national defense ,warindustry ,electricalvehicle , wireless communication, and consume e-lectronics .It is well known that the electrode ma-terial is the key factor to determine the perform-ance of supercapacitor . At present ,the activatedcarbonis the main marketed availa…     

透气防毒服用活性微球炭孔结构及其吸附性能

在实验室条件下研制了透气防毒服用石油沥青基球形活性炭（PSAC），采用扫描电子显微镜（SEM）对其形貌进行了观察，通过BET测定对PSAC的孔结构进行了表征，同时以苯和四氯化碳为吸附质研究了PSAC静态吸附性能，并与普通粒状活性炭（GAC）进行对比，比较了PSAC和GAC的二次吸、脱附性能．实验结果表明，PSAC的孔径分布主要以微孔为主，PSAC的吸、脱附速度较快，再生性能优异，是一种高性能的炭质吸附材料．     

应用模板法从煤沥青制备中孔活性炭

以煤沥青为原料,应用纳米二氧化硅模板法制备中孔活性炭,并考察焦模比、碱碳比以及活化温度对活性炭孔结构和收率的影响。结果表明,所得活性炭试样孔径分布最大值与模板剂孔径尺寸相吻合。在焦模比为2∶1、碱碳比为4.5∶1、活化温度为850℃时,所制活性炭总比表面积为1729 m^2/g,其中中孔比表面积为1702 m^2/g,占总比表面积的98.43%。     

Preparation and properties of pitch carbon based supercapacitor

Using the mesophase pitch as precursor, KOH and CO2 as activated agents, the activated carbon electrode material was fabricated by physical-chemical combined activated technique for supercapacitor. The influence of activated process on the pore structure of activated carbon was analyzed and 14 F supercapacitor with working voltage of 2.5 V was prepared. The charge and discharge behaviors, the properties of cyclic voltammetry, specific capacitance, equivalent serials resistance (ESR), cycle properties, and temperature properties of prepared supercapacitor were examined. The cyclic voltammetry curve results indicate that the carbon based supercapacitor using the self-made activated carbon as electrode materials shows the desired capacitance properties. In 1 mol/L Et4NBF4/AN electrolyte, the capacitance and ESR of the supercapacitor are 14.7 F and 60 m?, respectively. The specific capacitance of activated carbon electrode materials is 99.6 F/g; its energy density can reach 2.96 W·h/kg under the large current discharge condition. There is no obvious capacitance decay that can be observed after 5000 cycles. The leakage current is below 0.2 mA after keeping the voltage at 2.5 V for 1 h. Meanwhile, the supercapacitor shows desired temperature property; it can be operated normally in the temperature ranging from -40 ℃ to 70 ℃.     

核桃壳化学-物理耦合活化法制备活性炭及其表征

采用植物废弃物核桃壳为原料,以化学-物理耦合活化法制备了核桃壳活性炭,考察了磷酸浓度、活化温度、活化时间对核桃壳活性炭碘值、亚甲基蓝吸附值和烧失率的影响。结果表明,最佳制备条件为:磷酸质量分数85%,活化温度900℃,活化时间3h。在此制备条件下,核桃壳活性炭的比表面积为1 241.81m2·g-1,吸附累积总孔容为0.90cm3·g-1,最可几孔径分布为1.62nm。采用扫描电子显微镜、透射电子显微镜、比表面积测定仪以及红外光谱仪对核桃壳活性炭的表面形貌、孔结构及表面官能团进行了分析。     

Influence of nitrogen hetero-substitution on the electrochemical performance of coal-based activated carbons measured in non-aqueous electrolyte

Nitrogen-containing carbons were prepared by modification of activated carbons. The modified carbons were used as electrode materials with improved electrochemical performance. Precursor anthracite was activated by KOH (KOH: anthracite= 1:1), modified by melamine or urea and then treated at 1173 K to obtain the modified carbons. The porous structure, the chemical composition and the electrochemical characteristics of the carbons were investigated by nitrogen sorption, XPS and electrochemical methods respectively. Electrochemical experiments were performed in an organic electrolytic solution of 1 M (C2H5)4NBF4/PC.The samples modified by the different methods showed differences in chemical composition that introduced varying degrees of electrochemical performance enhancement. The presence of nitrogen enhanced the electron donor properties and the surface wettability of the activated carbons: this ensured a sufficient utilization of the exposed surface for charge storage.     

微孔活性炭纤维的制备及性能研究

以沥青基炭纤维为原料,采用（H2O＋CO2）物理活化的方法制备出微孔活性炭纤维（ACF）,研究了制备工艺对活性炭纤维微孔结构及性能的影响.结果表明：活化温度和时间对活性炭纤维比表面积影响较大;随着活化温度的升高,活性炭纤维的比表面积明显提高;在一定温度下活化时,活化初始阶段比表面积增加较快,活化一定时间后比表面积升高趋势变缓.铵盐浸渍处理加快了活化反应的进行,使活性炭纤维比表面积明显升高,孔径增大.     

Comparison of capacitive behavior of activated carbons with different pore structures in aqueous and nonaqueous systems

The pore structures of two activated carbons from sawdust with KOH activation and coconut-shell with steam activation for supercapacitor were analyzed by N2 adsorption method. The electrochemical properties of both activated carbons in 6 mol/L KOH solution and 1 mol/L EtgNPF4/PC were compared, and the effect of pore structure on the capacitance was investigated by cyclic voltammetry, AC impedance and charge-discharge measurements. The results indicate that the capacitance mainly depends on effective surface area, but the power property mainly depends on mesoporosity. At low specific current （1 A/g）, the maximum specific Capacitances of 276.3 F/g in aqueous system and 123.9 F/g in nonaqueous system can be obtained from sawdust activated carbon with a larger surface area of 1 808 m^2/g, butat a high specific current, the specific capacitance of coconut-shell activated carbon with a higher mesoporosity of 75.1% is more excellent. Activated carbon by KOH activation is fitter for aqueous system and that by steam activation is fitter for nonaqueous system.     

Preparation and electrochemical characterization of C/PANI composite electrode materials

1 INTRODUCTIONRecently , surpercapacitor has attracted greatattention for its unique power performance[1 ,2],while electrode materials ,as one key factor to de-termine the performance of supercapacitor , nowbecome the focus of many researches . The super-capacitor materials can be categorized into threetypes :carbon electrode materials[3], metal oxide e-lectrode materials[4]and conductive polymer elec-trode materials[5].Conductive polymer electrode materials havehigher capacitance than tha…     

Additivity of pore structural parameters of granular activated carbons derived from different coals and their blends

A series of granular activated carbons(GACs) were prepared by briquetting method from Chinese coals of different ranks and their blends,with coal pitch as the binder.Pore structural parameters including BET specific surface area(SBET),total pore volume(VT) and average pore diameter(da) were measured and calculated as well as process parameters such as yield of char(CY) and burn-off(B).The relationship between the pore structural parameters of the GAC from coal blend(BC-GAC) and the ones of the GACs from corresponding single coals(SC-GACs) was analyzed,in which an index,the relative error(d),was presented to define the bias between fitted values and experimental values of these parameters of the BC-GACs.The results show that the BC-GAC keeps qualitatively the pore structural features of the SC-GACs;as concerned as the quantitative relationship,the pore structural parameters of the BC-GAC from coal blend consisting of non-caking coals can be obtained by adding proportionally the pore structural parameters of the SC-GACs with d less than 10%.Meanwhile,for the BC-GAC from coal blend containing weak caking bituminous coal,the d increases up to 25% and the experimental pore size distribution differs greatly from the fitted one.     

Preparation of magnetically separable mesoporous activated carbons from brown coal with Fe_3O_4

Magnetically separable mesoporous activated carbon was prepared from brown coal in the presence of Fe_3O_4 as a bi-functional additive. Magnetic activated carbon(MAC) was characterized by lowtemperature nitrogen adsorption, scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and vibrating sample magnetometry(VSM). The evolution behaviors and transition mechanism of Fe_3O_4 during the preparation of MAC were investigated. The results show that prepared MAC with 6 wt% Fe_3O_4 addition having a specific surface area and mesopore ratio of 370 m~2·g~(-1) and 55.7%, which meet the requirements of adsorption application and magnetic recovery. Highly dispersed iron-containing aggregates with the size of 0.1 lm in the MAC were observed. During the preparation of MAC, Fe_3O_4 could enhance the escape of volatiles during the carbonization. Fe_3O_4 could also accelerate burning off the carbon wall during activation, which leads to enlarging micropore size, then resulting in the generation of mesopore and macropore. As a result, a part of Fe_3O_4 converted into FeO, FeOOH, a-Fe, c-Fe, Fe_2 SiO_4 and compound of Aluminum-iron-silicon.The prepared activated carbon, which was magnetized by both of residual Fe_3O_4, reduced a-Fe and cFe, can be easily separated from the original solution by external magnetic field.     

纳米门炭结构及超级电容特性

以生石油焦为原料,采用KOH活化法制备纳米门炭。采用氮气吸附法、X射线衍射(XRD)和光电子能谱衍射(XPS)对其孔结构、微晶结构和表面性质进行分析,并以其为电极组装超级电容器,测试了电容特性。结果表明:纳米门炭可在3.5V电压下工作,通过首次充电过程中的电化学活化而获得较大的比电容。样品N900比表面积仅为61m2/g,但比电容确高达136.7F/g,能量密度高达58.1Wh/kg。     

孔结构对煤基活性炭电化学性能的影响

以煤为前驱体,KOH为活化剂制备系列煤基活性炭电极材料.采用N_2吸附法及电化学测试对活性炭的孔结构和电化学性能进行了表征,研究了孔结构对活性炭电极材料的电化学性能的影响.结果表明,采用化学活化法可制备出比表面积1 048～3 581 m~2/g、中孔率7%～91%的活性炭电极材料.在3 mol/L KOH无机电解液体系及1 mol/L(C_2H_5)_4NBF_4/碳酸丙烯酯(PC)有机电解液体系中,活性炭电极材料的比电容分别达到322 F/g,190 F/g.2～3 nm的中孔对电解质离子在电极材料中的扩散有着重要作用,可以有效降低电解液的扩散阻力,提高电极材料比表面积的利用率,从而增强电容器的电化学性能.     

KOH活化杨木制备活性炭的特性研究

通过热重法对杨木颗粒以及用KOH浸渍后的杨木颗粒进行热解实验,通过TG、DTG、DSC曲线的变化规律,分析在主要失重阶段发生的物理变化、化学变化以及炭得率．结果表明：活化剂KOH中的K^＋对木材的热解具有催化作用．形成活性炭的温度基本为600℃,温度高于800℃时,活性炭发生烧失反应;升温速率对炭得率几乎没有影响;加入活化剂KOH后,提高了炭得率,但是炭得率与活化剂／杨木颗粒的质量比值成反比．     

不同变质程度无烟煤制活性炭的研究

本文根据对变质程度不同的阳泉、晋城、孤堰山３种无烟煤制作活性炭的研究，探讨了不同变质程度无烟煤制作活性炭的差异，从而对不同无烟煤原料加工活性炭工艺提出合理建议。认为低变质无烟煤（ＷＹ３）适宜生产活性炭，并可采用直接活化法生产合格破碎炭；中变质无烟煤（ＷＹ２）可得到合格的柱状炭，要生产破碎炭则需较高的活化条件；高变质无烟煤（ＷＹ１）不适宜制作活性炭。     

活性炭表面改性及其苯酚吸附性能研究

采用稀硝酸氧化和氮气气氛高温处理两种方法对市售活性炭进行表面改性,采用比表面分析仪、红外吸收光谱和Boehm滴定对改性前后活性炭进行表征,并测定活性炭对苯酚的吸附等温线,探讨影响活性炭对苯酚吸附能力的因素。结果表明：表面改性不仅增加了活性炭的比表面积和孔容,还改变了其表面化学性质。活性炭表面化学性质对苯酚吸附能力有着更重要影响,随着活性炭表面酸性官能团的增加,活性炭对苯酚吸附能力下降;酸性官能团数量减少,吸附能力增加。     

Eutectic effect during mesophase formation in co-carbonization of ethylene tar pitch and polystyrene

Ethylene tar pitch was co-carbonized with waste polystyrene to prepare mesophase pitch.The characteristics of mesophase pitches were examined using polarized light optical microscopy,apparent viscometr...     

Characteristics of activated carbon prepared from Chinese fir sawdust by zinc chloride activation under vacuum condition

The preparation of activated carbon from Chinese fir sawdust by zinc chloride activation under both nitrogen atmosphere and vacuum conditions was carried out in a self-manufactured vacuum pyrolysis reactor. The effects of the system pressure and the activation condition (nitrogen or vacuum) on pore development were investigated. The results show that both high quality activated carbon and high added-value bio-oil can be obtained simultaneously via vacuum chemical activation. The characteristics of the activated carbons produced under vacuum conditions are better than those prepared under nitrogen atmosphere. The performance parameters of the activated carbon obtained under vacuum conditions are as follows: the pore size distribution is mainly microporous, the Brunauer-Emmett-Teller (BET) surface area is 1 070.59 m²/g, the microporous volume is 0.502 4 cm³/g, the average pore size is 2.085 nm, and the iodine adsorption value and the methylene blue adsorption value are 1 142.92 and 131.34 mg/g, respectively. The activated carbon from vacuum chemical activation has developed micropores, and the N₂ adsorption equilibrium constant of the corresponding activated carbon gradually increases with the decrease of reaction system pressure.     

污泥活性炭的制备、结构表征及吸附特性

以城市污水厂污泥为原料,氯化锌为制孔剂,加入适当添加剂制备污泥活性炭,借助吸附等温线和BET、FT-IR、SEM等现代分析测试方法,表征其结构和吸附特性.结果表明:活化温度600℃、活化时间30 min、ZnCl2浓度50%、原料粒度20~24目时制备的污泥活性炭,其碘吸附值为643.0~815.6 mg/g,最可几孔径分布在4.16 nm左右,具有介空结构;平均孔容为0.4484~0.5122 mL/g,比表面积为634.8~748 m2/g,IR峰中C＝C、C—H、N＝O、C—OH是活性炭表面功能组.污泥活性炭对苯酚的吸附以多层吸附和毛细孔凝聚为主,微孔填满后达饱和,24 h饱和吸附量为15 mg/g.