Hierarchically Porous MnO2 Microspheres Doped with Homogeneously Distributed Fe3O4 Nanoparticles for Supercapacitors
详细信息 查看全文
- 作者：Jian Zhu ; Shaochun Tang ; Hao Xie ; Yuming Dai ; Xiangkang Meng
- 刊名：ACS Applied Materials & Interfaces
- 出版年：2014
- 出版时间：October 22, 2014
- 年：2014
- 卷：6
- 期：20
- 页码：17637-17646
- 全文大小：723K
- ISSN：1944-8252
文摘
Hierarchically porous yet densely packed MnO2 microspheres doped with Fe3O4 nanoparticles are synthesized via a one-step and low-cost ultrasound assisted method. The scalable synthesis is based on Fe2+ and ultrasound assisted nucleation and growth at a constant temperature in a range of 25鈥?0 掳C. Single-crystalline Fe3O4 particles of 3鈥? nm in diameter are homogeneously distributed throughout the spheres and none are on the surface. A systematic optimization of reaction parameters results in isolated, porous, and uniform Fe3O4鈥揗nO2 composite spheres. The spheres鈥?average diameter is dependent on the temperature, and thus is controllable in a range of 0.7鈥?.28 渭m. The involved growth mechanism is discussed. The specific capacitance is optimized at an Fe/Mn atomic ratio of r = 0.075 to be 448 F/g at a scan rate of 5 mV/s, which is nearly 1.5 times that of the extremely high reported value for MnO2 nanostructures (309 F/g). Especially, such a structure allows significantly improved stability at high charging rates. The composite has a capacitance of 367.4 F/g at a high scan rate of 100 mV/s, which is 82% of that at 5 mV/s. Also, it has an excellent cycling performance with a capacitance retention of 76% after 5000 charge/discharge cycles at 5 A/g.