Renewable Energy Global Innovations features: One-pot synthesis of hierarchical MnO2-modified diatomites for electrochemical capacitor electrodes

Significance Statement

The hierarchical and porous MnO₂-modified diatomite structures are prepared for the first time by a one pot hydrothermal method. We also demonstrate the synthesis of size- and shape-controlled MnO₂ nanostructures by replica molding from diatom silica structures for high-performance supercapacitors. The results show that birnessite-type MnO₂ nanosheets are observed to grow vertically on the purified diatomite, thus building hierarchical architecture. Three types of hierarchical hollow MnO₂ patterns with different three-dimensional (3D) structures, shapes and large surface areas were successfully prepared from three diatom species by a template-assisted hydrothermal process. The extraordinary precision and nano-scale resolution of 3D replications of complex biological architecture from diatoms to artificial MnO₂ structures are confirmed. The electrochemical results demonstrate that the MnO₂-modified diatomite electrode exhibits highly reversible features, good rate abilities, and good cycle stability (95.92% over 5000 cycles) demonstrating the suitability of the low-cost MnO₂-modified diatomite structure as a potential electrode material for supercapacitors. 

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

Journal of Power Sources. Volume 246, 2014, Pages 449-456.

Yu Xin Zhang ^1,2,*, Ming Huang¹, Fei Li¹ , their collaborators

Show Affiliations

1. College of Material 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

Abstract

The hierarchical and porous MnO₂-modified diatomite structures are prepared for the first time by a one-pot hydrothermal method. The morphology and structure of MnO₂-modified diatomite hierarchical structures are examined by focus ion beam scanning electron microscopy (FIB/SEM) and X-ray diffraction spectroscopy (XRD). The results show that Birnessite-type MnO₂ nanosheets are observed to grow vertically on the purified diatomite, thus building hierarchical architecture. Furthermore, the electrochemical properties of the MnO₂-modified diatomite electrodes are elucidated by cyclic voltammograms, galvanostatic charge/discharge tests and electrochemical impedance spectroscopy in 1 M Na₂SO₄ electrolyte. The electrochemical results demonstrate that the MnO₂-modified diatomite electrode exhibits highly reversible features and good rate abilities, respectively. Significantly, it exhibits the specific capacitance of 202.6 F g^-1 for the MnO₂-modified diatomite and 297.8 F g^-1 for the MnO₂ nanostructures after etching the diatomite. The capacitance retention of 95.92% over 5000 cycles further indicates the suitability of the low-cost MnO₂-modified diatomite structure as a potential electrode material for supercapacitors.

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