利用流體化床製備活性碳球於超級電容之應用

Abstract

本研究以酚醛樹脂球為原料合成出具高比表面積之球狀活性碳(ACS)，並應用於超級電容之碳電極材料，以測試球形多孔材料之電容表現。酚醛樹脂球經高溫碳化(500oC，1 小時)後，利用流體化床進行不同條件之二氧化碳物理活化(700–900oC，1–4 小時)；本研究同時透過反應曲面法(Response surface methodology)結合中央合成設計實驗(Central composite design)來探討不同活化條件下對於球狀碳孔結構發展之影響。結果顯示在900oC，4 小時的活化條件下，材料比表面積可達3142 m2g-1，孔體積可達1.513 cm3 g-1，孔徑分布則位於微孔與中孔之間。掃描式電子顯微鏡(SEM)觀察結果顯示合成之材料皆具有高度圓球率。超級電容之碳電極由不同活化條件下之球狀碳以及不同比例之黏著劑製備而成，組成二極式系統元件，以比較孔結構對於電容表現之影響。結果顯示，使用具高比表面積(3142 m2 g-1)與具較大之孔徑分布(2–3 nm)，並添加5 wt.%的黏著劑，可製備出具最佳電容表現之碳電極，其比電容值於1 M H2SO4 中為143.65 F g-1。在穩定性測試中，經過200 次充放電後，其充放電效率可接近100%，顯示其良好之循環性。整體而言，本研究探討不同條件下以流體化床活化球狀碳之比較以及其產物應用於超級電容之可行性。

In this study, activated carbon sphere (ACS) prepared with different activation conditions using a fluidized bed reactor was investigated, and the as–resulted ACSs were fabricated into carbon electrodes to examine the capacitive performance as a supercapacitor. The response surface methodology (RSM) was combined with the central composite design (CCD) to investigate the effects of different activation conditions on pore structure development. The results showed that the ACS activated at 900oC for 4 h possessed the highest specific surface area (3142 m2 g-1) and the greatest pore volume (1.513 cm3 g-1), and the pore size distribution was between micropore and mesopore ranges. Scanning electron microscopy (SEM) analysis revealed good sphericity of ACSs. The carbon electrodes were prepared from ACSs under different activation conditions with different percentage of binder, and their capacitive performance was evaluated through a two–electrode system cell. The results showed that the optimal carbon electrodes could be obtained using ACS with high specific surface area (3142 m2 g-1) and large pore size distribution (2–3 nm) and adding 5 wt.% binder. The specific capacitance was 143.65 F g-1 in 1 M H2SO4. In the cycling stability test, the charge/discharge efficiency could remain near 100% after 200 cycles, showing a good cyclability. Overall, this study explores the comparison of the ACS prepared under different activation conditions using a fluidized bed reactor and the feasibility of resulting ACS for supercapacitors.