【作者】 张小凤；

【导师】 李大光；

【作者基本信息】 广东工业大学 ， 化学工程， 2012， 硕士

【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。更多还原

【Abstract】 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.更多还原