In this study the focus was on the electrochemical techniques and aspects behind the
establishment of the better catalyst (platinum or gold) for the sulphur dioxide oxidation
reaction (SDOR). One of the primary issues regarding the SDOR is the catalyst material,
thus the comparative investigation of the performance of platinum and gold in the SDOR, as
found in this study. Ultimately, the SDOR could lead to an effective way of producing
hydrogen gas, which is an excellent energy carrier.
The electrochemical application of the oxygen reduction reaction (ORR) and ethanol
oxidation reaction (EOR) is an integral part of the catalytic process of water electrolysis, and
by using fuel cell technology, it becomes even more relevant to this study and can therefore
be used as a control, guide and introduction to the techniques required for electrochemical
investigation of catalyst effectiveness. Subsequently, the EOR as well as the ORR was used
as introduction into the different electrochemical quantification and qualification techniques
used in the electrochemical analyses of the SDOR.
Considering the ORR, gold showed no viable activity in acidic medium, contrarily in alkaline
medium, it showed good competition to platinum. Gold also lacked activity towards the EOR
in acidic medium compared to platinum, with platinum the best catalyst in both acidic and
alkaline media. Ultimately, platinum was established to be the material with better activity for
the ORR with gold a good competitor in alkaline medium, and platinum the better catalyst for
the EOR in both acidic and alkaline media.
With the main focus of this study being the SDOR, gold proved to be the best catalyst in salt
and gaseous forms of SO2 administration compared to platinum when the onset potential,
maximum current density, Tafel slope and number of electrons transferred are taken into
consideration. The onset potential was determined as 0.52 V vs. NHE for both platinum and
gold using SO2 gas and 0.54 V and 0.5 V for gold and platinum respectively, using Na2SO3
salt. The maximum current density using gaseous SO2 for platinum at 0 RPM was 400
mA/cm2 with a Tafel slope of 891 mV/decade whereas gold had a maximum current density
of 300 mA/cm2 and a Tafel slope of 378 mV/decade. Using Na2SO3 salt, the maximum
current density of gold was 25 mA/cm2 with a Tafel slope of 59 mV/decade whereas
platinum only achieved 18 mA/cm2 with a Tafel slope of 172 mV/decade. Concerning the
number of electrons transferred, gold achieves a transfer of 2 while platinum only 1 for both
SO2 gas and Na2SO3 salt. Taking all these summarised determinations into account, gold
was established to be a very competitive catalyst material for the SDOR, compared to
platinum. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2015
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/15579 |
| Date | January 2015 |
| Creators | Steyn, Marthinus Hendrik |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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