【作者】 彭佳；

【导师】 牟其伍；

【作者基本信息】 重庆大学 ， 材料物理与化学， 2006， 硕士

【摘要】 未经过表面处理的碳纤维表面能低,约为2.7×10-3 N/m,表面呈现憎液性,缺乏有化学活性的官能团,限制了碳纤维作为电极材料的应用。70年代中期发展起来的化学修饰电极(Chemically Modified Electrode,简称CME),为碳纤维电极的制备提供了新的思路。它是通过在电极表面进行分子设计,将具有优良特性的分子、离子、聚合物固定在电极表面,改变电极和电解液界面的微结构,使电极具有良好的电催化性能。CME丰富了电极材料,为直接氧化处理有机物开辟出新的途径。本文通过实验发现:采用0.5mol L-1磷酸溶液,2.0A/g的电流密度,通电5min电化学氧化处理的碳纤维为最佳方案。氧化处理后碳纤维接触角下降了约16o,表面能增加了近9倍,与环氧树脂基体粘接性能提高了33%,电化学响应明显改善。这些实验说明了电化学氧化改性是有效的手段,它使得碳纤维表面接上了数量丰富的活性官能团。通过红外光谱确定碳纤维表面接上的活性官能团主要为内酯基、羧基和羟基。系统讨论了未处理碳纤维在无机酸、无机盐和碱溶液中的电化学性质,表明碳纤维在酸性溶液中氧化最剧烈,中性溶液中的氧化较弱,碱性溶液的变化几乎可以忽略,说明选取磷酸电化学氧化碳纤维是合理的途径。分析了处理后碳纤维的电化学行为,0.5V氧化峰反映出纤维表面一些化学键发生了断裂,表面活性碳原子增加,表面已有的一些官能团被进一步氧化;0.19V氧化峰是纤维表面活性碳原子和吸附的氢氧根离子发生电化学氧化所致。实验还发现,处理后的碳纤维对电极分析标准溶液K4Fe(CN)6加KCl混合溶液、FeSO4加HClO4混合溶液有良好的电化学响应,是适合作为电化学分析的电极。将处理后的碳纤维和碳纳米管电极应用于水溶液中低浓度苯酚(低于5m mol L-1)的检测和氧化处理,发现碳纤维和碳纳米管电极可以在较低的电位(1.0VvsSCE)实现连续氧化,能克服电极吸附。恒电位氧化显示,碳纤维在1200s内保持了电极活性,能有效降低水溶液中的苯酚含量;碳纳米管电极在6000s之后仍然能保持活性,能逐渐将苯酚氧化直到完全清除。分析苯酚的氧化路径显示,苯酚被直接氧化为CO2,避免了二次污染,这证明了碳纤维和碳纳米管作为电极材料,在对污水中苯酚处理方面有应用前景。更多还原

【Abstract】 Carbon fiber without any modification can be hardly at its best due to the low surface energy, about 2.7×10-3 N/m, hydrophobic property and the lack of active functional groups. Chemically Modified Electrode(CME), which has got developed since the mid 70’s, can fix useful molecules, ions, and polymers onto the surface of electrode by molecular design to remodel the micro-structure of electrode and electrolytic interface, so that the electrode can be of fabulous catalyst.. CME enriches electrodes and exploits a new way to realize water treatment through oxidation approach.Through experiment, this paper claims that the optimal method of improving carbon fiber is to oxidize it for 5min in 0.5/mol L-1 H3PO4 solution with 2.0A/g current intensity. After treatment, the contact angle degree degreases by about 16o,the surface energy increases by nearly 9 times, and the adhesion to epoxy-resin is enhanced by 33% and the electrochemical response has been greatly improved, which demonstrates that the surface of carbon fiber is modified by fixing abundance of active functional groups, mainly lactone, hydroxyl and carboxyl confirmed by FT-IR spectra. Besides, this paper has discussed the electrochemical properties of carbon fiber in the solution of acid, salt, alkali and points out that the most intense oxidation occurs in acid solution, followed by neutral solution (salt), and the oxidation in alkali solution is totally negligible. All these data fully prove that it’s reasonable to use H3PO4 solution to oxidize carbon fiber electrochemically. The electrochemical properties of treated carbon fiber show that the 0.5V anodic peak has relation with bond breaking, active carbon atom increasing and functional groups oxidation, while 0.19V anodic peak demonstrates active carbon atoms react with adsorbent hydroxyls.In our experiment, the oxidized carbon fiber is found to be fine electrode for electrochemical analysis owing to its good response to K4Fe(CN)6 + KCl solution and FeSO4+HClO4 solution. Furthermore, it is noticed that both carbon fiber electrode and carbon nanotube electrode can be used to detect and oxidize aqueous phenol of low concentration (no more than 5m mol L-1) on a basis of low oxidation (1.0VvsSCE) that occurs continuously without electrode adsorption. The activity of Carbon fiber electrode can be kept for 1200s, during which phenol decreases dramatically, while that of carbon nanotube electrode is able to last 6000s, during which phenol is oxidized into CO2更多还原