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A high-rate aqueous symmetric pseudocapacitor based on highly graphitized onion-like carbon/birnessite-type manganese oxide nanohybrids

  • We present a study on the pseudocapacitive properties of birnessite-type MnO 2 grafted on highly graphitized onion-like carbon (OLC/MnO 2 ). In a three-electrode setup, we evaluated two different substrates, namely a platinum disc and nickel foam. The OLC/MnO 2 nanohybrid exhibited a large specific capacitance (C sp ) of 295 and 323 F g -1 (at 1 A g -1 ) for the Pt disc and Ni foam, respectively. In addition, the Ni foam substrate exhibited much higher rate capability (power density) than the Pt disc. A symmetrical two-electrode device, fabricated with the Ni foam, showed a large C sp of 254 F g -1 , a specific energy density of 5.6 W h kg -1 , and a high power density of 74.8 kW kg -1 . These values have been the highest for onion-based electrodes so far. The device showed excellent capacity retention when subjected to voltage-holding (floating) experiments for 50 h. In addition, the device showed a very short time constant ([small tau] = 40 ms). This high rate handling ability of the OLC/MnO 2 nanohybrid, compared to literature reports, promises new opportunities for the development of aqueous-based pseudocapacitors.

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Document Type:Article
Author:Katlego Makgopa, Paul M. Ejikeme, Charl J. Jafta, Kumar Raju, Marco ZeigerORCiD, Volker PresserORCiD, Kenneth I. Ozoemena
Parent Title (English):Journal of Materials Chemistry A
First Page:3480
Last Page:3490
Year of first Publication:2015
Date of final exam:2014/12/15
Release Date:2022/11/18
Impact:08.262 (2015)
Funding Information:This work was funded by the CSIR as well as the South Africa's Department of Science and Technology (DST) and National Research Foundation (NRF) under the “Nanotechnology Flagship Programme” (supercapacitors and fuel cell project, Grant no: 69849). German Federal Ministry for Research and Education (BMBF) in support of the nanoEES3D project (award number 03EK3013) as part of the strategic funding initiative energy storage framework.
Research Departments:Energie-Materialien
Open Access:Open Access
Signature:INM 2015/15
Licence (German):License LogoCreative Commons - CC BY - Namensnennung 4.0 International