Thesis (M.Sc. (Chemistry)) -- University of Limpopo, 2015 / The study has focused on the effects of different acids treatments on the
nanostructure of MWCNTs; doping metal oxides (copper oxide (CuO), Iron (III) oxide
(Fe2O3), nickel oxide (NiO) and cobalt oxide (Co3O4)) on MWCNTs and investigates
their electrochemical hydrogen and energy storage capabilities. Fourier transform
infrared (FTIR) confirmed the formation of functional groups on the surface of the
acid treated MWCNTs. X-ray diffraction (XRD) showed that the graphitic structure of
the MWCNTs was retained after treatment with mild acids (nitric acid (HNO3),
hydrogen peroxide (H2O2), a mixture of the acids, hydrogen peroxide: nitric acid
(H2O2:HNO3) and hydrogen peroxide: sulfuric acid (H2O2:H2SO4)). Transmission
electron microscopy (TEM) confirms the removal of bamboo carbon structures inside
the inner tubes of the MWCNTs after treatment with mild acids. Brunauer-Emmet-
Teller (BET) showed an increase in the surface area of mild acids treated MWCNTs.
Thermogravimetric analysis (TGA) results demonstrated that the thermal stability of
MWCNTs increases after treatment with mixtures of the acids.
Different metal oxides treated at different temperatures were incorporated into
MWCNTs (treated by a mixture of H2O2:HNO3). X-ray diffraction (XRD), scanning
electron microscopy (SEM) and Transmission electron microscopy (TEM) confirmed
the presence of different metal oxides inside/on the surface of the acid treated
MWCNTs.
The MWCNTs treated by H2O2:HNO3 gave both the highest discharge capacity
(72.63 mAh/g) and capacitance (8.61 F/g), as compared to the other electrode
materials. The improved hydrogen storage capacity and specific capacitance can be
attributed to high surface area, wider pore size distribution and the amount of
functional groups on the surface of H2O2:HNO3-treated MWCNTs; with the functional
groups acting as electron transmitters. The 5wt.% CuO@300oC-MWCNTs composite
showed the highest hydrogen storage capacity of 159 mAh/g. This capacity was
further improved by addition of manganese oxide resulting in the highest discharge
capacity of 172 mAh/g (which is equivalent to 0.64 wt.% of hydrogen stored). The
highest specific capacitance of 9.70 F/g was obtained on 5wt% Fe2O3@400oCMWCNTs
composite.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ul/oai:ulspace.ul.ac.za:10386/1439 |
| Date | January 2015 |
| Creators | Mkhondo, N. B. |
| Contributors | Magadzu, T. |
| Publisher | University of Limpopo |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | xx, 135 leaves |
| Relation |
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