SO2 - An indirect source of energy

Global sulphur dioxide (SO2) emissions peaked around the mid- 1970s, after which they declined. However, with the growth of specifically China, emissions are on the rise again. In 2008, global anthropogenic SO2 emissions totalled 127 Mt, with energy production accounting for 63.2 Mt and metal-related processes 12.8 Mt.

As a well-known gaseous pollutant, SO2 is not per se known as a source of energy. However, in the presence of water SO2 can be electro-oxidized at the anode of an electrolyser to produce hydrogen ions, which in turn can be reduced at the cathode of the electrolyser to produce hydrogen gas. Gaseous emissions of SO2 can therefore be cleaned up with the simultaneous production of hydrogen, an energy store or carrier, which provides an economic offset to the overall cost of this potential remediation process.

This process forms part of the Hybrid Sulfur (HyS) cycle as well as the once-through HyS (OTHyS) cycle. Indications are that the greatest stride towards the development of an effective electrolyser for the electro-catalytic oxidation of SO2 requires the development of an anode electrocatalyst exhibiting enhanced activity for the electro-oxidation of SO2.

A critical review will be presented on the research and development of such an anode electrocatalyst, and a strategy for a more effective research and development effort will be discussed. This will include theoretical studies on the electro-catalytic oxidation of SO2 on different metalbased catalytic surfaces (for which some preliminary results are presented) in conjunction with combinatorial (simultaneous multimetal multi-electrode) electrochemistry studies as well as singleelectrode electrochemistry studies.