One-pot synthesis of hierarchical MnO2-modified diatomites for electrochemical capacitor electrodes

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. (C) 2013 Elsevier B.V. All rights reserved.