The gradual depletion of and dependence on fossil fuels, air pollution and global
warming have all accelerated the development of alternative energy systems which use
hydrogen as an energy carrier. The hybrid sulphur cycle (HyS) is the foremost electrothermochemical
process that can produce hydrogen as the energy carrier.
The HyS cycle consists of two units, namely the sulphuric acid decomposition reactor
and the sulphur dioxide electrolyser (SDE). The SDE is responsible for the SO2 electrooxidation
to sulphuric acid and protons at the anode and the electro–reduction of
protons to hydrogen at the cathode. This research study focuses on the kinetic data
collected from the prepared catalysts for SO2 electro–oxidation at the anode.
Platinum dispersed on carbon, niobium pentoxide, tantalum pentoxide and zirconium
dioxide as electrocatalysts were prepared using sodium borohydride as a reducing
agent. These electrocatalysts were characterized using transmission electron
microscopy and x–ray diffraction. Cyclic voltammetry was used to study the
electrochemical active surface area (EAS) and the results showed that Pt/ZrO2–C had a
higher EAS area than Pt/Ta2O5–C, Pt/Nb2O5–C and Pt/C. The high EAS of Pt/ZrO2–C
can be explained by the low crystal size however after a series of linear polarisation
scans Pt/ZrO2–C experiences a much greater area loss than all the other catalysts.
Linear polarisation scans for each of the catalysts revealed that the influence of
increased temperature and sulphuric acid concentration were showed improved
results. Levich and Koutecky–Levich plots revealed that the SO2 oxidation is a multistep
reaction on all the prepared catalysts and that there are regions which are kinetic and
diffusion controlled and diffusion–only controlled. Pt/Ta2O5–C catalysts exhibited
superior catalytic activity and stability compared Pt/Nb2O5–C, Pt/ZrO2–C and Pt/C. The
Pt/ZrO2–C exhibited the most inferior catalytic activity and stability. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2011.
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/5557 |
| Date | January 2011 |
| Creators | Modingwane, Boitshoko Goitseone |
| Publisher | North-West University |
| Source Sets | North-West University |
| Detected Language | English |
| Type | Thesis |
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