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 NaSO<sub>4sub> solution, the capacitance of diamond EDLC is in the range of 3.6鈥?.0 渭F cm<sup>鈥?sup>, 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<sup>鈥?sup>, 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 MnO<sub>2sub> film to construct a pseudosupercapacitor. The MnO<sub>2sub> films were electrodeposited at a constant potential of 0.9 V vs Ag/AgCl in 0.2 M MnSO<sub>4sub> solution. The mass of MnO<sub>2sub> deposited per unit area, called the area density, calculated from the deposition charge, was controlled via the deposition time. The MnO<sub>2sub> films were characterized using various techniques like SEM, XPS, Raman spectroscopy, etc. In 1.0 M NaSO<sub>4sub> solution, the capacitance of the MnO<sub>2sub>/diamond-based pseudosupercapacitor rises with an increase of the mass of MnO<sub>2sub> on diamond. Its maximum capacitance was found to be reached at a MnO<sub>2sub> area density of 24 渭g cm<sup>鈥?sup>. The capacitance obtained from voltammetry is 384 渭F, or 326 F g<sup>鈥?sup> at a scan rate of 10 mV s<sup>鈥?sup>, which is comparable with the value of 406 渭F, or 349 F g<sup>鈥?sup>, obtained from charge/discharge process at a current density of 3 A g<sup>鈥?sup> 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<sup>鈥?sup>. The comparison of the performance of the MnO<sub>2sub>/diamond pseudosupercapacitor with that of those pseudosupercapacitors based on MnO<sub>2sub> and other carbon materials indicates that diamond could be suitable for electrochemical supercapacitor applications.