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Oxygen‐modified multiwalled carbon nanotubes: physicochemical properties and capacitor functionality
Author(s) -
Mombeshora Edwin T.,
Ndungu Patrick G.,
Jarvis A. L. Leigh,
Nyamori Vincent O.
Publication year - 2017
Publication title -
international journal of energy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.808
H-Index - 95
eISSN - 1099-114X
pISSN - 0363-907X
DOI - 10.1002/er.3702
Subject(s) - cyclic voltammetry , dielectric spectroscopy , fourier transform infrared spectroscopy , electrolyte , raman spectroscopy , carbon nanotube , oxygen , chemical engineering , electrochemistry , chemistry , materials science , thermogravimetric analysis , analytical chemistry (journal) , nanotechnology , electrode , organic chemistry , engineering , physics , optics
Summary Multiwalled carbon nanotubes (MWCNTs) have found numerous applications in energy conversion systems. The current work focused on the introduction of oxygen moieties onto the walls of MWCNTs by five different reagents and investigating the associated physicochemical properties. Oxygen‐containing groups were introduced onto MWCNTs using an ultrasound water‐bath treatment with HNO 3 , HCl, H 2 O 2 or HCl/HNO 3 solution. Physicochemical properties were characterised by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman, thermal gravimetric analysis, textural characteristics, cyclic voltammetry and electrochemical impedance spectroscopy. The study focus was mainly on linking the physicochemical properties of oxygen‐functionalised MWCNTs and suitability in electrochemical capacitors using group one sulfates. From the Fourier transform infrared spectroscopy KBr pellet protocol, peaks at 3400, 2370 and 1170 cm −1 suggest oxygen‐containing functionalities on MWCNTs. HNO 3 treatment introduced highest oxygen‐containing moieties and achieved highest specific capacitance in Li 2 SO 4 and Na 2 SO 4 electrolytes of 36.200 F g −1 (77 times better than pristine) and 45.100 F g −1 (2.5 times enhancement), respectively. For K 2 SO 4 , it was 33.600 F g −1 (4.9 times better) with HNO 3 /HCl‐treated samples. Oxygen‐functionalised MWCNTs displayed both pseudo and electrochemical double‐layer mechanism of enhanced charge storage and cycle stability in group one sulfates electrolytes. The dominating charge storage mechanism was pseudo, and Na 2 SO 4 was the best electrolyte amongst the three group one sulfates investigated. Copyright © 2017 John Wiley & Sons, Ltd.