聚苯胺/量子點複材之製備、性質及在超級電容之應用

本論文利用化學聚合的方式在石墨箔碳材上成長導電高分子聚苯胺(PANI)作為超級電容的電極。首先以不同濃度苯胺氧化聚合24小時形成PANI，由SEM觀測到PANI表面形態，並以TGA量測電極上PANI的重量，FTIR鑑定表面官能基，再以各式電化學量測，包括恆電流充放電、循環伏安法和交流阻抗分析來鑑定電容特性；發現以0.01M合成的PANI結構為奈米針狀陣列且擁有最大的比表面積及最佳的比電容值，在1A/g電流密度下電容值為740.54 F/g，20 A/g下為286.22 F/g；此最佳化的條件將作為製備後續吸附量子點的PANI電極，量子點材料包括石墨烯量子點及氧化釕量子點，希望能增進電極的電容表現。實驗採用改良後的Hummers法，以100°C，120°C，140°C三種反應溫度製備出尺寸不同，氧化程度也不同的GQDs-1，GQDs-2，GQDs-3。從TEM觀測得到平均尺寸分別為7nm，4nm，3.5nm；DLS觀察到的平均尺寸為7.7 nm，4.7nm，3.3 nm，兩者結果差不多；由AFM得知GQDs-1，GQDs-3為1-3層堆疊，而GQDs-2濃度較高有1-5層堆疊出現；三種GQDs以PL測量，隨激發波長的增加放射波長均產生紅移；由UV證實在280nm及340nm均有一吸收峰，此結果和PLE互相呼應；由XPS及反射式 FTIR鑑定出，以GQDs-3的C=O峰值最低，還原程度最高造成導電性上升；由反射式 FTIR 得知3256cm-1 的primary amine峰值增強亦證明GQDs成功吸附PANI產生氫鍵，使1211cm-1和1267 cm-1的C-N鍵訊號被遮蔽。在電性方面，GQDs-3/PANI電極在1 A/g下電容值為907.38 F/g，在20A/g下仍有315.32 F/g，為三種GQDs吸附後電容表現最好的電極；透過CV圖積分面積計算亦證明GQDs-3/PANI比電容值最高，代表GQDs-3的導電性較好；由阻抗分析發現GQDs吸附PANI電極均能使的電荷轉移電阻(Rect)下降，增進電極介面的氧化還原反應。此外，實驗利用水熱法製備RuO2結晶水合物，以量子點形式吸附於PANI電極表面以增進電容值。從TEM得知RuO2量子點平均尺寸為4nm，和DLS觀察相近；由FTIR證明在502cm¬-1，608 cm¬-1有Ru的特徵峰，且RuO2因含有結晶水會和PANI產生大量氫鍵，從3401cm-1的涵蓋含水的O-H的特徵峰非常寬可見得；由TEM觀測到RuO2量子點成功吸附在PANI表面；而製備的RuO2/PANI複合電極電容值在1 A/g下為1098.14 F/g，在20A/g下為504 F/g；且隨電流密度的增加，RuO2/PANI電極的電容表現比GQDs-3/PANI更好；由Ragone plot結果顯示三極式RuO2/PANI和GQDs-3/PANI在1A/g電流密度，功率密度為350W/kg下，能量密度分別為74.72、61.73Wh/Kg。最後，實驗採用比電容表現最佳GQDs-3 /PANI及RuO2/PANI複合電極，搭配GO/EMITFSI電解質組裝成二極式作為商用電容器。經過4wt%氧化石墨稀(GO)摻雜EMITFSI離子液體時比電容值達到最佳化，RuO2/PANI、GQDs-3/PANI其值在1 A/g時，為231.21 F/g，192.79 F/g。透過1000次充放電長效循環測試，結果顯示二極式RuO2/PANI電極的電容保持率為58.2%，電容保持率比三極測試來的高。由Ragone plot結果顯示，在1A/g電流密度，功率密度為350W/kg下，二極式RuO2/PANI 和GQDs-3/PANI為15.72、13.12 Wh/Kg。

關鍵字

超級電容；聚苯胺；化學沉積；可撓石墨箔；石墨烯量子點；氧化釕；氧化石墨烯；離子液體

並列摘要

This thesis utillized the chemical oxidation method to synthesize the polyaniline (PANI) nanowires in array on graphite foil employed for supercapacitor electrodes. First, after polymerized for 24 h with different concentration of aniline, the surface morphology was investigated by SEM, mass weight on graphite foil was estimated by TGA, and surface functional groups were characterized by FTIR-ATR. Electrochemical measurements including Galvanostatic charge discharge, cyclic voltammetry and electrochemical impedance were employed to characterize their specific capacitance. When the concentration of aniline was 0.01 M, the PANI nanowire array showed the highest surface area with the optimized specific capacitance reaching 740.54 F/g at 1 A/g, and 286.22/g at 20 A/g. The optimized electrodes were then used to adsorb the quantum dot materials including graphene quantum dots (GQDs) and ruthenium oxide(RuO2) for further studies. The modified Hummers method was used to fabricate the GQDs-1, GQDs-2, GQDs-3 by varying the hydrothermal reaction temperature at 100°C, 120°C and 140°C, respectively for 12 h. Their sizes of 7, 4, and 3.5 nm measured by TEM were similar to those measured by DLS (7.7 nm for GQDs-1 , 4.7 nm for GQDs-2. and 3.3 nm for GQDs-3 ). The PL spectra showed that with increasing the excitation wavelength, the emission peak shifted to longer wavelengths. AFM observations revealed that GQDs-1 and GQDs-3 consisted of 1~3 layers in contrast to 1~5 layers for GQDs-2. According to the XPS results, the percentage of C=O bonds decreased with higher reaction temperature, which is consistant with the FTIR observation. Furthermore, the ATR-FTIR also revealed that the peak intensity at 3256 cm-1 contributed by primary amine increased as hydrogen bonds formed between GQDs and PANI, leading to the disappearance of C-N bonds peak. Next, the GQDs/PANI electrodes were prepared by immersing PANI electrodes in diluted GQDs suspension. By dipping PANI electrode in 1 mg/ml GQDs, the best performance of GQDs-3/PANI electrode was obtained with the specific capacitance reaching 907.38 F/g at 1 A/g, and 315.32 F/g at 20A/g, which are also supported by the CV data. EIS measurements confirmed that the electron charge transfer resistances for PANI electrode were decreased significantly as the PANI electrode was incorporated with GQDs-3. Hydrous RuO2·xH2O quantum dots were fabricated by hydrothermal process. The average particle size was about 4 nm as estimated by TEM, similar to the DLS measurement. As they were adsorbed by PANI, the FTIR spectrum showed that the peak at 3485cm-1 became broader, indicating the formation of hydrogen bonds between RuO2·xH2O and PANI. As to the performance of RuO2/PANI electrodes, the best specific capacitance of RuO2/PANI electrode reached to 1098.14 F/g at 1 A/g and 504 F/g at 20A/g, which are better than that of the GQDs-3/PANI electrodes. The energy density of RuO2/PANI electrode reached to 74.72 Wh/kg with 350W/kg power density at 1 A/g compared to 61.73Wh/kg for GQDs-3/PANI electrodes. Two-electrode confuguration supercapapcitor were also fabricated by using GO/EMITFSI ionic liquid composite electrolyte system. When 4 wt% of GO was incorporated with EMITFSI, the electrolyte system became immovable. RuO2/PANI and GQDs-3/PANI electrodes showed the best specific capacitance of 231.21 and 192.79 F/g, respectively at 1 A/g. After charge-discharge test for 1000 cycles, two-electrode configuration with RuO2/PANI electrode can retain 58.2% specific capacitance, better than that with three-electrode configuration. From the Ragone plot, the energy density reached to 15.72 Wh/Kg for RuO2/PANI electrode compared to 13.12 Wh/Kg for GQDs-3/PANI electrodes in two-electrode system.

並列關鍵字

Supercapacitor ； Polyaniline ； Chemical Deposition ； Flexible Graphite Foil ； Graphene Quantum Dots ； Ruthenium Oxide ； Graphene Oxide ； Ionic Liquid

參考文獻

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聚苯胺/量子點複材之製備、性質及在超級電容之應用

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