Fabrication of manganese dioxide nanosheet-based thin-film electrode and its electrochemical capacitance performance

A manganese dioxide (MnO2) nanosheet-based thin film deposited on a conductive Ni substrate has been synthesized via a hydrothermal route. Field emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) showed that the as-prepared thin film had a porous network structure, which consisted of interlaced MnO2 nanosheets oriented perpendicular to the substrate. Electrochemical tests demonstrated that the MnO2 nanosheet-based thin-film electrode exhibited excellent capacitance performance with high rate properties and good cycling stability. A specific capacitance of 385 Fg(-1) was obtained at a current density of 0.5 A g(-1), with a capacitance retention of about 81% when the current density was increased from 0.5 to 5 A g(-1). When cycled at a higher current density of 1.25 A g(-1), 93% of the initial specific capacitance was retained over 5000 cycles. The excellent electrochemical properties of this MnO2 thin-film electrode can be attributed to its thin-sheet morphology, porous structure and the good contact between the MnO2 active material and the Ni substrate. Considering the excellent performance and facile preparation, this thin-film electrode should have great potential for application in energy storage and conversion devices. (C) 2012 Elsevier Ltd. All rights reserved.