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论文类型：期刊论文

发表时间：2011-04-07

发表刊物：JOURNAL OF PHYSICAL CHEMISTRY C

收录刊物：Scopus、SCIE、EI

卷号：115

期号：13

页面范围：5413-5421

ISSN号：1932-7447

摘要：Nanostructured mesoporous manganese oxides were easily prepared by mixing KMnO(4) with ascorbic acid in an aqueous solution under ambient conditions. The obtained manganese oxides were identified as having an alpha-MnO(2) tunnel structure composed of an edge-shared network of [MnO(6)] octahedra. TEM observations revealed that the obtained MnO(2) materials had three-dimensional frameworks which consisted of homogeneous nanoparticles with sizes of ca. 5 nm. Nitrogen sorption analyses showed that these MnO(2) nanoparticles exhibited a type IV isotherm, indicating a mesoporous character. Large surface areas up to 284 m(2) g(-1) were recorded. The electrochemical performances of the synthesized alpha-MnO(2) nanoparticles as supercapacitor electrode materials were studied using cyclic voltammetry and galvanostatic charge-discharge cycling in a three-electrode system at a potential range from 0 to 1.0 V vs a saturated calomel electrode in 0.5 M sodium sulfate solution. The result showed that mesoporous MnO(2) with three-dimensional frameworks exhibit a high capacitance up to similar to 200 F g(-1). Furthermore, a hybrid supercapacitor was assembled by using MnO(2) mixed with a small amount of activated carbon as the positive electrode and activated carbon as the negative electrode in a 0.5 M Na(2)SO(4) electrolyte. By balancing the mass of MnO(2) and activated carbon, a practical cell voltage of 1.8 V could be obtained in aqueous medium with a capacitance of 23.1 F g(-1). After 1200 cycles, the maximum energy density is 104 Wh kg(-1) and power density is 14.7 kW kg(-1). Thus, the obtained alpha-MnO(2) nanoparticles are suitable for use as supercapacitor electrode materials.