Renewable Energy Global Innovations features: Self-Assembly of Mesoporous Nanotubes Assembled from Interwoven Ultrathin Birnessite-type MnO2 Nanosheets for Asymmetric Supercapacitors

Significance Statement

 Here, we develop a simple and cost-effective approach to prepare CuO@MnO₂ core-shell nanostructures without any surfactants and ultrathin MnO₂ nanosheets-built nanotubes have been fabricated via a large-scale chemical etching method. An asymmetric supercapacitor with CuO@MnO₂ core-shell nanostructure as the positive electrode and activated microwave exfoliated graphite oxide (MEGO) as the negative electrode yields an energy density of 22.1 Wh kg^-1 and a maximum power density of 85.6 kW kg^-1; the device shows a long-term cycling stability which retains 101.5% of its initial capacitance even after 10000 cycles. The MnO₂ nanotubes in a three-electrode system display much high specific capacitance (377.5 F g^-1 at current density of 0.25 A g^-1), good rate performance.

Moreover, an asymmetric supercapacitor on the basis of MnO₂ nanotubes as the positive electrode and activated graphenes (AG) as the negative electrode produced an energy density of 22.68 Wh kg^-1 and a maximum power density of 4.5 kW kg^-1. Such a facile strategy to fabricate the hierarchical CuO@MnO2 core-shell nanostructure and MnO₂ nanotubes with significantly improved functionalities opens up a novel avenue to design electrode materials on demand for high-performance supercapacitor applications. 

About The Author

Dr. Yu Xin Zhang received his B. Eng. and M. Eng. in Chemical Engineering from Tianjin University in 2000 and 2003, respectively. He received his Ph.D degree in Chemical and Biomolecular Engineering from the National University of Singapore (NUS) in 2008, and continued to work as a research fellow in Prof. Hua Chun Zeng’s group at NUS till 2009. Now Dr. Zhang is a full professor of College of Materials Science and Engineering in Chongqing University. Dr. Zhang’s research interest is self-assembled nanostructures for energy storage materials and photocatalysts. 

Journal Reference

Scientific Reports. Volume 4:4518, 2014.

Ming Huang¹, Yuxin Zhang^1,2, Fei Li¹, Lili Zhang³, Rodney S. Ruoff⁴, Zhiyu Wen² , Qing Liu¹

Show Affiliations

1. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, P.R. China,

2. National Key Laboratory of Fundamental Science of Micro/Nano-Devices and System Technology, Chongqing University, Chongqing 400044, P.R. China,

3. Institute of Chemical and Engineering Sciences, A*STAR, 1 Pesek Road, Jurong Island 627833, Singapore, Department of
4. Mechanical Engineering and the Materials Science and Engineering Program, The University of Texas at Austin, One University Station C2200, Austin, Texas 78712, United States.

Abstract

Porous nanotubes comprised of MnO2 nanosheets were fabricated with a one-pot hydrothermal method using polycarbonate membrane as the template. The diameter and thickness of nanotubes can be controlled by choice of the membrane pore size and the chemistry. The porous MnO2 nanotubes were used as a supercapacitor electrode. The specific capacitance in a three-electrode system was 365 F g21 at a current density of 0.25 A g21 with capacitance retention of 90.4% after 3000 cycles. An asymmetric supercapacitor with porous MnO2 nanotubes as the positive electrode and activated graphene as the negative electrode yielded an energy density of 22.5 Wh kg21 and a maximum power density of 146.2 kW kg21; these values exceeded those reported for other MnO2 nanostructures. The supercapacitor performance was correlated with the hierarchical structure of the porous MnO2 nanotubes.

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