Aspect ratio controlled growth of MnOOH in mixtures of Mn3O4 and MnOOH single crystals for supercapacitors

Single crystals of MnOOH and Mn3O4 were synthesized through a simple sol-gel route. From transmission electron microscopy. Fourier transform infrared, X-ray diffraction, and selected area electron diffraction analyses, manganese oxides prepared in this work are demonstrated to be a mixture consisting of MnOOH and Mn3O4 single crystals. The relative amount of MnOOH in the mixture gradually increased with increasing aspect ratio of the MnOOH nanorods. The aspect ratio controlled growth of MnOOH nanorods without using templates is predictable by an equation correlated with the preparation variables. Thick coatings of manganese oxides with this novel structure are demonstrated to show capacitive-like characteristics for the supercapacitor applications. (C) 2005 The Electrochemical Society.