Electrochemical Synthesis and Supercapacitive Properties of epsilon-MnO2 with Porous/Nanoflaky Hierarchical Architectures

A facile electrochemical method involving a hydrogen coevolution cathodic electrodeposition followed by an in situ electro-oxidation progress has been developed to prepare epsilon-MnO2 with a porous/nanoflake hierarchical architecture. Characterizations show that the cathodic-electrodeposition process produces porous spinel Mn3O4, while the subsequent in situ electro-oxidation progress rapidly and completely transforms the spinel Mn3O4 to the epsilon-MnO2 in nanoflakes without the destruction of the porous matrix. epsilon-MnO2 deposits with a porous/nanoflake hierarchical architecture have been found with a high specific capacitance of 320 F g(-1) for the 1st cycle (0.125 F cm(-2)) and 307 F g(-1) for the 2000th cycle. The deposits convey an energy density of 24.4 Wh kg(-1) at a power density of 4500 W kg(-1). The porous manganese oxide with good and stable electrochemical performance can be the promising candidate for supercapacitors. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3133247] All rights reserved.