Undoped and doped activated carbons derived from phenylphenol precursors and their electric storages via double layer capacitance

• Main Authors: Chun-Wei Chiang, 江俊緯
• Other Authors: Dah-Shyang Tsai
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/5gdh9s

碩士 === 國立臺灣科技大學 === 化學工程系 === 106 === In this study, a low-cost chemical phenylphenol has been implemented as the precursor of activated carbon for electrochemical capacitor applications. The energy storage capability of this activated carbon is further enhanced by doping of B and N. In undoped activated carbon, the specific surface area of the activated carbon can be increased by raising the pyrolysis temperature and the amount of the pore-forming potassium agents, and the pore size also become larger and more. The molar ratio of phenylphenol to potassium increased from 1:1.5 to 1:20, specific surface area increased from 948 m2 g-1 to 2528 m2 g-1, when para-phenylphenol is used as a precursor at 900C; specific surface area increased from 1323 m2 g-1 to 1740 m2 g-1, when ortho-phenylphenol is used as a precursor. The specific capacitance can be greater than 200 F g-1, using a high specific surface area undoped activated carbon at scan rate of 0.5 mV s-1 in 0.5 M H2SO4(aq). The specific capacitance exceeds 400 F g-1 at scan rate of 1 mV s-1 in 1 M TEABF4 in ACN. Also it displays good cycle stability. Boron-doped activated carbon obtained after incorporation of 5% boric acid, regardless of the molar ratio of phenylphenol to potassium is 1:12 or 1:20, both achieve a larger specific surface area than undoped activated carbon, the specific surface area can be up to 2609 m2 g-1, and the pore also tends to increase in size. The specific capacitance of the boron-doped activated carbon is 316.6 F g-1 at scan rate of 0.5 mV s-1 in 0.5 M H2SO4(aq). The specific capacitance is 509.7 F g-1 at a scan rate of 1 mV s-1 in 1 M TEABF4 in ACN. The specific surface area is up to 2659 m2 g-1, when the amount of boric acid is increased to 10%, the specific surface area and pores are more enhanced than 5% boron. The specific capacitance of the boron-doped activated carbon is 344.7 F g-1 at scan rate of 0.5 mV s-1 in 0.5 M H2SO4(aq). The specific capacitance is 521.3 F g-1 at a scan rate of 1 mV s-1 in 1 M TEABF4 in CAN, regardless of whether the doping amount of boron is 5% or 10%, and it shows good cycle stability. After doping with nitrogen, the activated carbon obtained through pyrolysis at 900C, the specific surface area reaches 3000 m2 g-1 or more, and the amount of mesoporous pores is raised as well. Nitrogen-doped activated carbon is measured with specific capacitance more than 500 F g-1 at scan rate of 0.5 mV s-1 in 0.5 M H2SO4(aq). Specific capacitance more than 550 F g-1 can be obtained at a scan rate of 1 mV s-1 in 1 M TEABF4 in ACN, and the cycle stability is also excellent, but the yield is less than 20%. Finally, two different electrolytes (TEABF4 and TBABF4) and five different pore size distributions of activated carbon were used to study the connections between different pore sizes on different ion sizes. We also find TBA+ hardly enter pores which the size is smaller than 1.5 nm, when comparing the difference in cyclic voltammetry curves measured from different electrolytes and the pore size distribution pattern.