奈米碳複合材料的表面作用力

Abstract

此論文主要探討奈米碳複合材料中的界面科學現象，其中包含兩種複合材料。 第一部份為單壁奈米碳管與共軛高分子複合材料。我們利用高分子作為分散劑以分散單壁碳管在有機溶劑中，發現高分子分子結構與溶劑種類對單壁碳管的分散性有很大的影響，研究顯示特定的高分子與有機溶劑組合，可以選擇性分散具有特定結構或半徑的單壁碳管。此外，激發光譜也顯示在高分子與碳管間有能量轉移的現象。 第二種複合材料為白金與多孔碳，以期用在燃料電池的應用上。實驗發現利用離子交換法可以得到均勻的奈米白金顆粒（2至3奈米），而白金總承載量則與白金鹽類和碳材料表面的電位有很大的相關性。界面電位分析顯示，在碳材料表面官能基整體表現的零電位點若越低，表示表面越傾向負電，則對使用具帶正電的白金錯合物鹽類，離子交換法成效越好。

In this work, two nano carbon composites have been prepared and characterized. Conjugated polymers were used as dispersing agents for preparing single-walled carbon nanotubes (SWCNTs) solutions in organic solvents. It is found that the dispersion results of nanotubes are affected greatly by the polymer structure and solvent. With more flexible polymer backbone structure, more nanotube species can be observed by photoluminescence. That is, less selectivity this polymer behaves. Among three solvents we investigated, chloroform though gave the highest solubility, the evidences show that most of dispersed nanotubes remain bundles, which is unwanted. THF gave the second highest and toluene the lowest. However, the low solubility enhances the chance of selectivity. A strong chiral angle preference in favor of armchair structure has been observed in PFO/toluene solutions and diameter preference around 1.05 nm is obtained when PFO is replaced with PFO-BT. These results suggest the possibility for bulk purification of SWCNTs by using designated polymer/solvent combinations. The second composite, carbon-supported platinum (Pt) is aiming for fuel cell applications, in which the carbon materials were fabricated by polymer blend method and Pt nanoparticles were loaded with ion-exchange technique. Porous properties of carbon supports are found to be dependent on the carbonization conditions and mixed-polymers’ ration and a carbon support with mesoporous structure and surface area up to 441 m2/g is obtained; the dispersion and loading amount of deposited Pt are related to the Pt precursors and the surface acidity of carbon supports. An uniform particle size distribution around 2~4 nm and a loading amount of 16 wt% with exchange efficiency as high as 82% were achieved by this method, which is of sufficient requirements for fuel cells. Besides, the zeta potential curve can also be used to monitor the suitable pH region for ion-exchange reactions and to predict the loading amount of catalyst.