1-丁基-1-甲基吡咯啶水楊酸根室溫離子液體的電化學探討與電化學還原法製備鈀奈米粒子之研究

本論文之研究利用電化學、質譜以及理論計算探討1-butyl-1-methylpyrrolidinium salicylate (BMP-SAL) 離子液體之負電位極限。實驗結果證明BMP-SAL離子液體之還原電位極限是決定於SAL-陰離子的還原而非BMP+陽離子之還原反應。理論計算結果則說明了實驗所獲得之結論。此部分研究顯示傳統上認為離子液體的負電位極限是由組成離子液體之陽離子的還原反應所主導的觀念是不正確的，在使用及解釋離子液體內之電化學反應時，應更加謹慎小心。本研究並使用此離子液體為電解質，以電化學還原法製備Pd奈米粒子(Pd NPs)。探討溶液溫度、Pd前趨物濃度、介面活性劑hexadecyltrimethylammonium chloride (CTAC)、hexyltrimethylammonium bromide (HeTAB)以及樹枝狀分子(G3 PAMAM dendrimer)的添加對Pd NPs形成的影響。利用SEM、TEM、XRD鑑定所製備的Pd NPs。發現利用較高溫度、濃度所獲得的Pd NPs晶體較小，但顆粒大小分佈較不均勻，而添加介面活性劑製備出的Pd NPs則大小顆粒分布較為均勻；添加G3 dendrimer雖然獲得之Pd NPs晶體較小但有著嚴重的聚集，推測可能是由於G3 dendrimer表面含有大量NH2官能基與離子液體的SAL-產生氫鍵作用力導致聚集。利用所獲得的Pd NPs直接連同離子液體與導電石墨粉混合後塗布於網版印刷碳電極上製作成複合電極，於1 M NaOH中利用循環伏安法、流體動力安培法以及Tafel plot探討此種複合電極電催化¬氧化乙醇分子的效能。結果顯示利用提高溫度以及濃度所製備出的Pd NPs對於乙醇氧化的電催化效率優於市售之Pd觸媒，添加G3 dendrimer所製備之Pd NPs可能由於大量聚集使得催化效率差；而添加介面活性劑雖然可以產生出均勻的Pd NPs顆粒大小但對於乙醇電催化反應卻遜色於市售Pd觸媒，其原因還需進一步研究。

關鍵字

鈀；離子液體；奈米粒子

並列摘要

In this thesis, the cathodic limit of the new room temperature ionic liquid 1-butyl-1-methylpyrrolidinium salicylate (BMP-SAL) was studied by cyclic voltammetry (CV), proton nuclear magnetic resonance spectroscopy (H-NMR), and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). The experimental data indicate that the cathodic limit of BMP-SAL is determined by the reduction of SAL reduction rather than the reduction of BMP+ cation. The theoretical calculations support the experimental data, and the results indicate that anion reduction-dominated cathodic limit should be a common phenomenon in ionic liquids. To explain the electrochemical behavior occurring in ionic liquids must be cautiously because, traditionally, the reduction of cations that compose the ionic liquid is believed to determine the cathodic limit of ionic liquids. On the other hand, BMP-SAL was used as the electrolyte for the preparation of Pd nanoparticles (PdNPs) by electrochemical reduction of PdCl2. The effects of solution temperature, surfactants such as hexadecyltrimethylammonium chloride (CTAC) and hexyltrimethylammonium bromide (HeTAB), and G3 PAMAM dendrimer on the formation of PdNPs were studied. The PdNPs were characterized with transmission electron microscope (TEM), scanning electron microscope (SEM) and powder X-ray diffraction (XRD). It shows that PdNPs with smaller crystal size were obtained at higher temperature and concentraction. However, the size distribution of the PdNPs are widely than that of PdNPs obtained in the existence of surfactants. Introducing dendrimer causes serious aggregation of PdNPs and it may result from the hydrogen bonding among the large number of NH2 groups of dendrimers and SAL- anions. The electrochemically active surface area (ECSA) of the ionic liquid-graphtie-Pd nanoparticles (IL-GP-PdNPs) electrodes was determined based on the reduction wave of Pd oxide in 1 M sodium hydroxide using CV. CV and hydrodynamic amperometry (HA) were used for studying the electrocatalytic oxidation of ethanol at the IL-GP-PbNPs electrodes. The PdNPs prepared in this study show better electrocatalytic activity toward ethanol oxidation than that of the commercial catalyst (ETK-Pd/C, 20 wt% at active carbon).