세공이 조절된 EDLC용 셀룰로오스계 활성탄소섬유 제조 및 그 전기화학적 특성

다국어 초록 (Multilingual Abstract)

To improve the electrochemical performance, we prepared eco-cellulose based activated carbon fibers by heat treatment and chemical activation for electric double layer capacitor (EDLC). The carbon fibers were chemically activated using potassium hydroxide, phosphoric acid and sodium hydroxide to increase specific surface area and develop pores. To investigate the surface morphology of the resultant samples, SEM images were obtained by using a field emission scanning electron microscope. The textural properties of the activated samples were investigated using a volumetric adsorption apparatus to determine the pore structure based on effects of chemical activation. The effects of various kinds of activation on carbon fibers and their electrochemical properties were investigated. The electrochemical characterization of activated carbon fibers was performed with a Compactstat Electrochemical Interface with a three-electrode assembly. Cyclic voltammetry measurements of the electrode materials were performed over a potential range of 0 – 1 V at scan rates of 5 and 50 mV/s. All the electrochemical measurements were performed in a 1 M H2SO4 electrolyte solution. The KOH activation samples showed the highest specific capacitance and the lowest retained capacitance ratio because it has the highest specific surface area and micropore volume without mesopore. The H3PO4 activation samples indicated decreased specific capacitance because it is ineffective in development of micropore. But retained capacitance ratio of H3PO4 activation samples was enhanced rather than KOH activation samples. The specific capacitances of 4 M NaOH activation samples were enhanced to 159, 148 F/g at scan rate 5, 50 mV/s, respectively. Furthermore, 4N-CCF indicated the largest retained capacitance ratio of 93%. The enhancement of specific capacitances and retained capacitance ratio was attributed to an increase in the mesopore volume with high specific surface area caused by the activation of the reaction between the carbon fibers surfaces and sodium hydroxide. These results demonstrated that a sodium hydroxide activated carbon fibers-based electric double layer capacitor electrode effectively enhanced specific capacitance and retained capacitance ratio than potassium hydroxide and phosphoric acid.

목차 (Table of Contents)

• 1.서론 1
• 2.이론적 배경 4
• 2.1.전기 이중층 커패시터(EDLC) 4
• 2.1.1.EDLC의 정의 및 특성 4
• 2.1.2.EDLC의 구조 및 충·방전 원리 6
• 2.2.셀룰로오스(cellulose) 섬유 10
• 2.2.1.셀룰로오스 분자구조 특성 10
• 2.2.2.셀룰로오스의 화학반응 14
• 2.2.3.라이오셀(lyocell) 섬유 15
• 2.3.다공성 탄소재료 18
• 2.3.1.세공구조 및 특성 18
• 2.3.2.탄소재료의 활성화 21
• 2.3.3.흡착과 탈착 22
• 2.3.4.흡착등온선 23
• 2.4.전기화학분석 (cyclic voltammatry) 29
• 2.4.1.CV의 원리 및 특성 29
• 2.4.2.주사속도에 따른 영향 32
• 3.실험 및 분석 33
• 3.1.시료 및 시약 33
• 3.2.셀룰로오스계 탄소섬유의 제조 및 활성화 33
• 3.3.EDLC용 전극 제조 34
• 3.4.특성 분석 34
• 3.4.1.표면 특성 분석 34
• 3.4.2.비표면적 및 기공특성 분석 35
• 3.4.3.전기화학적 특성 분석 35
• 4.결과 및 고찰 37
• 4.1.KOH 활성화에 따른 활성탄소섬유의 특성 37
• 4.1.1.표면특성 37
• 4.1.2.비표면적 및 기공특성 39
• 4.1.3.전기화학적 특성 44
• 4.2.H3PO4 활성화에 따른 활성탄소섬유의 특성 49
• 4.2.1.표면특성 49
• 4.2.2.비표면적 및 기공특성 51
• 4.2.3.전기화학적 특성 56
• 4.3.NaOH 활성화에 따른 활성탄소섬유의 특성 60
• 4.3.1.표면특성 60
• 4.3.2.비표면적 및 기공특성 62
• 4.3.3.전기화학적 특성 67
• 5.결론 71
• 참고문헌 73