Applications of nitrogen-doped reduced graphene oxide on electrochemical capacitor

• Main Authors: Jing-ya Wong, 翁靖雅
• Other Authors: Dah-shyang Tsai
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/06898999496283423889

碩士 === 國立臺灣科技大學 === 化學工程系 === 102 === This study explores the capacity of nitrogen doped reduced graphene oxide (N-doped rGO) in the asymmetric electrolyte [EMI][TFSI]. We employ the Staudenmaier method to exfoliate and reduce the graphene oxide, and find the sample of N-doped rGO owns a surface area, higher than 1100?aC undoped rGO. Hence, the capacitor investigation focuses on how to make most of the electrochemical window of [EMI][TFSI] with N-doped rGO. The electrochemical window of [EMI][TFSI] is measured between -1.65 and +2.6 V (vs. RHE) with platinum electrodes. Another window rarely mentioned in the literature is the intercalation window, which is -1.6 V the lower window limit and +1.2 V (vs. RHE) the upper window limit for N-doped rGO. If we charge/discharge the capacitor in the working window of 2.0 V, the positive and negative potentials vary within the intercalation window. Consequently, the electrode capacitance ratio of positive and negative electrode is near the ratio measured with cyclic voltammetry, assuming energy storage depends on double layer capacitance entirely. When we impose the 3.8 V working window without considering a proper mass balance, we often found the negative electrode exceeds -1.65 V and decomposes the electrolyte. Careful analysis of the electrode potential variations indicates the main restriction is on the negative potential, therefore, the mass ratio of positive over negative (M+/M-) ought to be less than 1 to use the lopsided potential window sufficiently. The capacitor performance of an M+/M- ratio 0.736 is investigated with details.