Electrochemical synthesis and supercapacitive properties of ε -MnO2 with porous/nanoflaky hierarchical architectures

Abstract

A facile electrochemical method involving a hydrogen coevolution cathodic electrodeposition followed by an in situ electro-oxidation progress has been developed to prepare ε -MnO2 with a porous/nanoflake hierarchical architecture. Characterizations show that the cathodic-electrodeposition process produces porous spinel Mn3 O4, while the subsequent in situ electro-oxidation progress rapidly and completely transforms the spinel Mn3 O4 to the ε -MnO2 in nanoflakes without the destruction of the porous matrix. ε -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. © 2009 The Electrochemical Society.