Electrochemical Supercapacitors from Diamond

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• 作者：Siyu Yu ; Nianjun Yang ; Hao Zhuang ; Jan Meyer ; Soumen Mandal ; Oliver A. Williams ; Inga Lilge ; Holger Sch枚nherr ; Xin Jiang
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：August 20, 2015
• 年：2015
• 卷：119
• 期：33
• 页码：18918-18926
• 全文大小：555K
• ISSN：1932-7455

文摘

Boron-doped diamond has been utilized as an electrode material to construct an electric double layer capacitor (EDLC) as well as an electrode support to form a pseudocapacitor. In 1.0 M NaSO₄ solution, the capacitance of diamond EDLC is in the range of 3.6鈥?.0 渭F cm^鈥?, comparable with those of EDLCs based on other carbon materials. During a charge/discharge process for 1000 cycles at a scan rate of 100 mV s^鈥?, the capacitance only decreases 5%, indicating high stability and a long lifetime of such an EDLC. To improve the capacitance of diamond EDLCs, diamond was coated with a MnO₂ film to construct a pseudosupercapacitor. The MnO₂ films were electrodeposited at a constant potential of 0.9 V vs Ag/AgCl in 0.2 M MnSO₄ solution. The mass of MnO₂ deposited per unit area, called the area density, calculated from the deposition charge, was controlled via the deposition time. The MnO₂ films were characterized using various techniques like SEM, XPS, Raman spectroscopy, etc. In 1.0 M NaSO₄ solution, the capacitance of the MnO₂/diamond-based pseudosupercapacitor rises with an increase of the mass of MnO₂ on diamond. Its maximum capacitance was found to be reached at a MnO₂ area density of 24 渭g cm^鈥?. The capacitance obtained from voltammetry is 384 渭F, or 326 F g^鈥? at a scan rate of 10 mV s^鈥?, which is comparable with the value of 406 渭F, or 349 F g^鈥?, obtained from charge/discharge process at a current density of 3 A g^鈥? in the potential range 0 to 0.8 V. The capacitance was reduced by 34% after 1000 subsequent charge/discharge cycles carried out at a scan range of 100 mV s^鈥?. The comparison of the performance of the MnO₂/diamond pseudosupercapacitor with that of those pseudosupercapacitors based on MnO₂ and other carbon materials indicates that diamond could be suitable for electrochemical supercapacitor applications.