摘要
碳纳米管具有接近理想的一维纳米空间、优异的电化学性能而广泛地应用在储氢材料、催化剂载体以及电子器件等领域。开口的碳纳米管既可以直接作为超级电容器电极材料,又可以在中空管腔内填充金属及其氧化物;且填充后的复合材料也可以作为超级电容器电极材料,并且改善电容性能。本文采用液相湿化学法首先对碳纳米管提纯、开口,并利用处理后的碳纳米管内填充外来物质氧化锰,最后研究开口的碳管和内填充氧化锰碳管的电化学性能。
本文采用硝酸氧化回流法对碳纳米管进行纯化、开管处理,分别讨论了反应时间、硝酸浓度、反应温度对碳纳米管失重率的影响。通过分析对比处理前后碳纳米管的SEM可知,处理后碳纳米管的分散性更好,且管周围的颗粒消失,结合分析X射线衍射图谱发现回流后的碳管没有杂质NiO的特征峰,表明杂质颗粒在回流过程中已经完全除去。热重曲线表明酸氧化处理后,催化剂已经完全去除,但碳纳米管的抗氧化能力减弱。红外光谱表明处理后的碳纳米管含有—O-H、—C=O和—C-O极性官能团,这些官能团都能够提高碳纳米管在水中的分散性。
为了将外来物质氧化锰填充进入碳纳米管内,本文将开管的碳纳米管和硝酸锰溶液混合搅拌,分别讨论了填充时间和硝酸锰浓度对填充率的影响。通过TEM分析可知,延长反应时间和增大硝酸锰浓度都有利于碳纳米管的填充。分析XRD图谱表明填充后的碳纳米管有氧化锰的特征峰。TG曲线表明,填充后的碳纳米管完全燃烧的残留物比开管后碳纳米管残留物质量分数增加了13%。
本课题将纯化后的碳纳米管和填充后的碳纳米管分别作为电极材料进行循环伏安测试和恒流充放电测试,分别讨论了扫描速度、硝酸处理时间以及硝酸浓度对碳纳米管电化学性能的影响。循环伏安曲线结果表明扫描速度越大,碳纳米管电极的比电容越小,这主要是由于质子从溶液迁移到电极中心需要一定的时间,且填充氧化锰的碳纳米管电极比电容增加。通过分析不同处理时间下碳纳米管的恒流充放电曲线表明,随着反应时间的增加,比电容增大,但当反应时间超过20h由于碳纳米管管壁及长短发生变化,导致碳纳米管的比电容明显减小;通过分析不同浓度硝酸处理后的碳纳米管电极的恒流充放电曲线表明,硝酸浓度为12mo1/L时,碳纳米管的工作电极比电容最大,而浓硝酸处理的碳纳米管电极比电容最小。
Carbon nanotubes widely used for hydrogen storage, catalytic carrier and electronic devices materials because it have perfect1D nano-space and excellent physical and chemical properties. Opened carbon nanotubes can be used for supercapacitor materials and be filling other substance in it. The filled CNTS can also be used for supercapacitor electrode materials, which has high performance. In this study, the MWCNTS was purified and opened the tips of the CNTS via wet chemistry method. The opened CNTS was filled with manganese oxide, then test the electrochemical performance of the opened CNTS and the filled CNTS.
In this paper, the carbon nanotubes are refluxed in nitric acid in order to purify and open the tips of the CNTS, discussing the relative affected factor to the weight loss of the CNTS, which include the reaction time, the molar concentration of the nitric acid and the temperature. The pretreated MWCNTS have improved the dispersion than the raw CNTS when compared to the two scanning electron microscopy images. In addition, there were no spots around CNTS shown in the SEM image. Meanwhile the purified MWCNTS and raw MWCNTS were characterized by XRD diffraction. Except the peaks corresponding to the structure of raw MWCNTS, some peaks with comparatively visible diffraction broadening disappeared in purified MWCNTS, the peaks could be indexed as NiO. From the TG curve analysis, we also found the purified MWCNTS have successfully remove the catalyst particles, yet the antioxidation have been weaken. The pretreated MWCNTS with HNO3have allowed—O-H,—C=O and—C-O polar functional groups to attach the surface of the MWCNTS,which have improved and improved the dispersion of MWCNTS.
In order to introduce manganese oxide into the hollow cavity of the opened M-WCNTS, the pretreated MWCNTS are stirred in manganous nitrate for some times. we discuss the relative affected factor to the filling rate of the CNTS, which include the reaction time, the molar concentration of the manganous nitrate. From the TEM image, we found the manganese oxide have successfully filled into the hollow cavit-y of the opened MWCNTS. The filling rate improve with the increase of the reactio n time and the concentration of the manganous nitrate. The filled MWCNTS were c h-aracterized by XRD diffraction. Some new peaks with comparatively visible diffract ion broadening occurred in purified MWCNTS, the peaks could be indexed as MnO2. The residues of the MnO2/MWCNTS have increased percent13than the purified o nes, which also demonstrate the MnO2filled into MWCNTS successfully.
The Cyclic voltammetry and Galvanostatic charge/discharge curve are used to investigate the electrochemical behavior of the samples. From the analysis of the CV curve, both purified MWCNTS electrodes and filled MWCNTS electrodes are evaluated in alkaline at different scan rates respectively. The results show that the specific capacitance of the electrodes decrease with the increasing of the scan rate, because the exchanging of the proton from the electrolyte to the electrodes need some times,therefore the higher scan rate is,the lower specific capacitance. In addition, the filled MWCNTS electrodes have higher specific capacitance than the pretreated MWCNTS. From the analysis of galvanostatic charge/discharge curve in different reaction time and different pretreated concentration nitric aric, we found that the specific capacitance improved with the increase of the reaction time, while the specific capacitance decreased when the reaction time reach to20h. Meanwhile pretreated by12mol/L nitric acid for24h have higher specific capacitance than the others.
引文
[1]Iijima S. Helical Microtubles of Graphitic Carbon[J]. Nature,1991,354:56-58.
[2]Iijima S, Ichihash T. Single shell carbon nanotubes OD 1nm diameter[J]. Nature, 1993,363:603-605.
[3]Hsu W.K, Zhu Y.Q, Tasoba. Solid-phase production of carbon nanotubes[J]. A ppl.Phys.A,1999,68:493-496.
[4]Hatta N, Murala K. Very long graphtic nanotubes synthesized by plasma decom-position of benzene [J]. Chem. Phys. Lett,1994,217:398-401.
[5]王敏炜,李凤仪,彭年才.合成碳纳米管的镍基催化剂中镧的作用[J].南昌大学学报(理科板),2002,26:381~385.
[6]林松,徐才录.催化剂中镍含量对CVD法制备碳纳米管的影响[J].炭素技术,2002,119:653~657.
[7]吕德义,徐铸德.催化剂活性组分的负载方法对CVD法制备碳纳米管的影响[J].无机化学学报.2001,17:775~779.
[8]Zhang Y.F, Gamo M.N, Xiao C.Y, et al. Liquid phase synthesis of carbon n a-notubes[J]. Physica,2002,323:293-295.
[9]田亚峻,谢克昌,樊友三.用煤合成碳纳米管新方法[J].高等学校化学学报,2001,22:1456~1458.
[10]Ren Z.F, Huang Z.P, JWXu, et al. Synthesis of large arrays of well aligned carbon nanotubes on glass[J]. Science,1998,282:1105-1105.
[11]董树荣,徐江平,王春生,等.催化热分解制备碳纳米管的研究[J].炭素材料,1998,3:28~33.
[12]朴玲钰,周兴政,陈久岭.A1203气凝胶负载催化剂催化甲烷裂解制备碳纳米管[J].四川大学学报(工程科学版),2002,5:42~46.
[13]卢锦花,阎鑫.碳纳米管制备技术的最新进展[J].炭素技术,2003,5:34~37.
[14]杨占红,李星海,陈志国,等.碳纳米管的纯化[J].材料导报,1999,13(3):29~30.
[15]Bandow S, Asaka S, Zhao X. Purification and magnetic properties of carbon nanotubes[J]. Appl Phys A.Materials Science&Processing,1998,67(1):23-27.
[16]张翼,齐暑华,王洲,等.碳纳米管纯化处理的研究进展[J].材料导报A:综述篇,2011,25(9):6~9.
[17]王敏炜,姚彦红,查少华,等.重铬酸钾用于碳纳米管开口及表面处理的研究[J].南昌大学学报.工科板,2006,28(1):1~3.
[18]孙晓刚,曾效舒.空气氧化法提纯碳纳米管的研究[J].新型碳材料,2004,19(1):65~67.
[19]周金梅,李海燕,林国栋,等.多壁碳纳米管的纯化及其表面含氧官能团的表征[J].物理化学学报,2010,26(11):3080~3086.
[20]王敏炜,彭年才,李凤仪.硝酸氧化法对碳纳米管进行纯化及开管的研究[J].江西科学,2002,20(4):203~206.
[21]赵红,宫丽红.单壁碳纳米管的纯化[J].哈尔滨师范大学自然科学学报,2007,23(2):78~81.
[22]张建国,宫丽红,郭丽华.硝酸法纯化碳纳米管的研究[J].化学工程师,2008,157(10):4-6.
[23]郭松林,徐小勇,邓爱平,等.纯化处理对CVD法制备的碳纳米管氧化行为的影响研究[J].中国陶瓷,2011,47(8):12~14.
[24]杨占红,李新海,李晶,等.碳纳米管纯化技术研究[J].中南工业大学学报,1999,30(4):389-391.
[25]余荣清,程大典,詹梦熊,等.液相化学腐蚀法用于碳纳米管的纯化及顶端开口研究[J].化学通报,1996,4:25~26.
[26]辛育东,刘晓东.碳纳米管酸氧化改性[J].东华理工大学学报(自然科学版),2010,33(1):75~78.
[27]郭振,方炎.单壁碳纳米管的快速、高效提纯方法研究[J].光散射学报,2009,21(1):59~63.
[28]刘耀鹏.液/气相综合氧化法纯化碳纳米管研究[J].新技术新工艺材料与表面处理技术,2007,4:82~84.
[29]耿叶静,雷江伟,晏善成,等.无定形碳纳米管的合成、表征及其纯化后的电化学性能[J].安徽工业大学学报,2009,26(3):271~274.
[30]杨占红,李新海,王红强,等.碳纳米管的提纯—重铬酸钾氧化法[J].化学世 界,1999,12:627~629.
[31]Heath J.R, Brien S.C.O Zhang Q. Lanthanum complexes of spheroidal carbon shells[J]. J.Am.Chem.Soc,1985,107:7779-7780.
[32]Pederson M.R, Broughton J.Q. Nanocapillarity in fullerene tubeles[J]. Phys.Rey. Lett,1992,69:2689-2692.
[33]吕瑞涛,黄正宏,康飞宇.金属填充碳纳米管的制备研究进展[J].材料科学与工程学报,2006,24(5):772~776.
[34]Ebbesen T.W. Wetting filling and decorating carbon nanotubes[J]. Phys.Chem. Solids,1996,57:951-955.
[35]Dujardin E, Ebbesen T.W, Hiura H. Capillaryity and wetting of carbon n-anotubes[J]. Science,1994,265:1850-1851.
[36]赵东林,郑重,李霞.Ag纳米粒子及Ag纳米线在碳纳米管上的沉积和填充[J].功能材料,2006,37:861~864.
[37]Li Jian-hua, Hong Ruo-yu, Luo Guo-hua, et al. An easy approach to encapsulating Fe3O4 nanoparticles in multiwalled carbon nanotubes[J]. New Carbon Materials, 2010,25(3):192-198.
[38]叶茂,周震,卞锡奎,等.CoO填充多壁碳纳米管作为锂离子电池负极材料[J].无机化学学报,2006,22(7):1307~1311.
[39]张颖,高学平,胡恒,等.无机化学学报,2004,20(9):1013~1016.
[40]曹慧群,魏波,梁讯.Fe3O4-γ/Fe2O3填充多壁碳纳米管的合成及磁性能[J].中国西部科技,2008,7(13):37~39.
[41]马若彪,付延鲍,马晓华.二氧化锡填充多壁碳纳米管材料的制备及电化学性能[J].物理化学学报,2009,25(3):441~445.
[42]Aldo Capobianchi, Sabrina Foglia, Patrizia Imperatori, et al. Controlled filling and external cleaning of multi-wall carbon nanotubes using a wet chemical met hod[J]. Carbon,2007,45:2205-2207.
[43]吴胜伟,刘士远,郭学金,等.同位素示踪法在碳纳米管填充行为研究中的应用[J].核化学与放射化学,2004,4(12):225~227.
[44]张拦,朱红,宋渊,等.稀土氧化物Nd2O3填充碳纳米管的微波吸收性能[J].北京交通大学学报,2008,32(6):4-5.
[45]张军辉,曹慧群,朱美芳,等.氧化亚锡填充碳纳米管的制备和表征[J].材料导报,2005,19:81-83.
[46]Wu Hua-Qiang, Wei Xian-Wen, Shan Ming-Wang, et al. Preparation of Fe-Ni alloy nanoparticles inside carbon nanotubes via wet chemistry[J]. Journalof materials chemistry,2002,1919-1921.
[47]Sharif Hussein Sharif Zein, Loon-Chong Yeoh, Siang-Piao Chai et al. ynthesis of manganese oxide/carbon nanotube nanocomposites using wet chemical method [J]. Journal of materials processing technology,2007:402-405.
[48]吕瑞端,康飞宇,黄正宏,等.填充α-Fe碳纳米管的电磁性能研究[J].无机材料学报,2008,23(1):23~28.
[49]李维学,崔永福,戴剑,等.电弧法合成填充金属的纳米粒子的碳纳米管[J].兰州理工大学学报,2007,33(1):162~165.
[50]Guerret piecourt C, Le Bouar Y, Loiseau A, et al. Relation between metal electronic structure and morphology of metal compounds inside carbon nanotubes [J]. Nature,1994,372:761-765.
[51]袁新生.纳米碳材料超级电容器电极的制备研究[D].广东工业大学,2011.
[52]王晓峰.碳纳米管超级电容器的研制和应用[J].电源技术,2005,29(1):27~30.
[53]Jurewicz K, Bable K, P ietrzak R, et al. Capacitance properties of multi walled carbon nanotubes modified by activation and ammoxidation[J]. Carbon,2006, (44):2368-2375.
[54]何春建,薛宽宏,陈巧玲,等.多壁碳纳米管阵列电极的循环伏安行为[J].化学研究,2003,15(5):628~629.
[55]Chen J H, Li W Z, Wang D Z, et al. Electrochemical characterization of carbon nanotubes as electrode in electrochemical double layer capacitors[J]. Carbon,2002, (40):1193-1197.
[56]张建宇,曾效舒,蔡结松.基于碳纳米管的双层电容器[J].南昌大学学报:工科版,24(3):14~15.
[57]Frackowiaka E, Metenier K, Bertagna V, ea al. Supercapacitor electrodes from multiwalled carbon nanotubes[J]. Appl Phys Lett,2000,77(15):2421-2423.
[58]Ankh, Jeon K.K, Heo J.K, et al. High capacitance supercapacitor using a nan-ocomposite electrode of single walled carbon nanotube and polypyrrole[J]. J Ele ctrochem Soc,2002,149(8):1058-1062.
[59]马仁志,魏秉庆,徐才录,等.基于碳纳米管的超级电容器[J].中国科学:E辑,2004,30(2):112~1165.
[60]江奇,卢晓英,赵勇,等.碳纳米管微结构的改变对其容量性能的影响[J].物理化学学报,2004,20(5):546~549.
[61]Melsheimer J, Ziegler D. Oxygen electrode reaction in acid solutions on RuO2 elecrtode prepared by the thermal decomposition methods[J]. Thin Solid Films, 1998,163:301-308.
[62]Pang S.C, Anderson M.A, Chapman T.W. Novel electrode material for thin film ultracapacitors:comparison of electrochemical properties of sol-gel derived and electrodeposited manganese dioxide[J]. J Electrochem Soc,2000,147:444-450.
[63]Xie xiaofeng, Gao lian. Characterization of a manganese dioxide/carbon nanotube composite fabricated using an in situ coating method[J]. carbon,2007,45: 2365-2373.
[64]邓梅根,杨邦朝,胡永达.活化和Mn02沉积提高碳纳米管超级电容器的性能[J].功能材料,2005,36(3):408~410.
[65]赵东林,李学良.超电容器碳纳米管与钼复合电极材料的研究[J].贵州化工2005,30(6):12~13.
[66]黄德如,汪仁庆.无机和配位化合物的红外和拉曼光谱[M].北京,化学工业出版社,1986.
[67]Zhang Hong-bin, Lin Guo-dong, Zhou Zhen-hua, et al. Raman spectra of MWCNS and MWCNT-based H2-adsorbing system[J]. Carbon,2002,40:2429-2436.
[68]Branca C, Frusteri F, Magazu V, et al. Characterization of carbon nanotubes by TEM and infrared spectroscopy[J]. J.Phys.Chem.B,2004,108:3469-3473.
[69]Eklund P.C, Holden M.J, Jishi R.A. Vibrational modes of carbon nanotubes; spectroscopy and theory[J]. carbon,1995,33(7):959-972.
[70]Dandekar A, Baker R.T.K, Vannice M.A. Characterization of activated carbon, graphitized carbon fibers and synthetic diamond powder using TPD and drifts [J]. Carbon,1998,36(12):1821-1831.
[71]Figueiredo J.L, Pereira M.F.P, Freitas M.M.A, et al. Modification of the surface chemistry of activated carbons[J]. carbon,1999,37:1379-1389.
[72]王正元,贾志杰,张增民.用红外光谱研究硝酸处理对多壁碳纳米管表面羧基的影响[J].炭素技术,1999(5):14-16.