A high-rate aqueous symmetric pseudocapacitor based on highly graphitized onion-like carbon/birnessite-type manganese oxide nanohybrids
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Date
Authors
Makgopa, Katlego
Ejikeme, Paul Madus
Jafta, Charl Jeremy
Raju, Kumar
Zeiger, Marco
Presser, Volker
Ozoemena, Kenneth I.
Journal Title
Journal ISSN
Volume Title
Publisher
Royal Society of Chemistry
Abstract
We present a study on the pseudocapacitive properties of birnessite-type MnO2 grafted on highly
graphitized onion-like carbon (OLC/MnO2). In a three-electrode setup, we evaluated two different
substrates, namely a platinum disc and nickel foam. The OLC/MnO2 nanohybrid exhibited a large specific
capacitance (Csp) 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 Csp 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 (s ¼ 40 ms). This high rate handling ability of the OLC/MnO2 nanohybrid, compared
to literature reports, promises new opportunities for the development of aqueous-based pseudocapacitors.
Description
Keywords
Birnessite-type manganese oxide nanohybrids, Onion-like carbon (OLC), Electrical double-layer capacitors (EDLCs), Pseudocapacitors
Sustainable Development Goals
Citation
Makgopa, K, Ejikeme, PM, Jafta, CJ, Raju, K, Zeiger, M, Presser, V & Ozoemena, KI 2015, 'A high-rate aqueous symmetric pseudocapacitor based on highly graphitized onion-like carbon/birnessite-type manganese oxide nanohybrids', Journal of Materials Chemistry A, vol. 3, no. 7, pp. 3480-3490.