MnO2 has been deposited onto two types of carbon (C) substrates, including a non-porous multi-wall carbon nano-tube (CNT) and a porous carbon black (CB) powder, by a solution reduction process where MnO4 - was reduced at 80 °C by the C substrate so as to give nano-crystalline MnO2 directly at the C surface. The nature of the C substrate has profound effects on polymorphicity, microstructure and electrochemical properties, in terms of supercapacitor application, of the resulting oxide. Deposition on CNT produces meso/macro-porous layer containing predominantly spinel MnO2 strongly bonded to the CNTs and having a larger surface area, while that on CB results in birnessite granules with a lower surface area. In addition to having a higher specific capacitance (309 F g-1), the MnO2/CNT electrode exhibits superior power performance (221 F g-1 at 500 mV s-1 or ca. 20 Wh kg -1at 88 kW kg-1) to MnO2/CB due to reduced electronic and ion-diffusion resistances. Furthermore, the MnO2/CNT electrode also exhibits slower self-discharging rate and greater cycling stability. The results indicate that the MnO2 spinel/CNT holds promise for supercapacitor applications. © 2011 Elsevier B.V. All rights reserved.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUK-C1-014-12
Acknowledgements: This work is partially supported by Taiwan Textile Research Institute, by National Science Council, Taiwan, ROC (NSC 98-2221-E-002-084-MY3 and 98-3114-E-007-011), and by King Abdullah University of Science and Technology (KAUST) under the GRP Award (award no. KUK-C1-014-12).
This publication acknowledges KAUST support, but has no KAUST affiliated authors.