Electricity from hydrogen sulfide, a common waste gas

Hydrogen sulfide (H2S), a waste gas with the advantages of low cost, easy storage and transportation, and high electrochemical activity, can be utilized as a fuel in PEM-based fuel cell system, thereby enabling H2S removal and electricity generation.

Article  |  Fall 2015

Hydrogen sulfide is a toxic, corrosive gas that occurs naturally or is generated by industrial activity. Hydrogen sulfide is generated in processes necessary for human survival, for example, in refining of petroleum for energy production and in anaerobic digestion processes for sewage treatment. The annual generation of hydrogen sulfide in the world is currently estimated to be 250 million tons and is expected to increase continuously. Thus, it is important to secure technology for effective removal of hydrogen sulfide.

The most common process for treating hydrogen sulfide is the Claus process. The Claus process shows a high hydrogen sulfide removal rate and, thus, is already widely used, but it has problems in terms of economics because it requires high initial installation costs and high-temperature and high-pressure operating conditions. In addition, hydrogen, an exhaust gas generated during the process, contains corrosive byproducts such as CS₂, SO₂, and COS and, thus, is not effectively used. Accordingly, a process is needed that can remove hydrogen sulfide while minimizing energy consumption, and if such a process could produce energy, that would be even more beneficial.

Accordingly, Prof. Han’s research group has made extensive efforts to solve the above-described problems, and as a result, have found that, if hydrogen sulfide is absorbed into an alkaline solution in a hydrogen sulfide removal process, it can be removed at a rate of 100%. Moreover, if the resulting solution containing produced sulfide ions is fed into the anode of a fuel cell, electricity can be produced. Additionally, it has been found that, if the alkaline solution containing sulfide ions is used as fuel, the fuel cell can continue its performance over a long period of time without poisoning the electrode, thereby demonstrating its durability without sulfur-induced poison.

This research was published in several papers in the International Journal of Hydrogen Energy (Vol. 39 7142-7146, 10493-10497, Vol. 40 2979-2983, 4141-4145, 4567-4572) and the Journal of Applied Electrochemistry (Vol. 45 533-539).

[Images from Prof. Han’s group]

For more information: http://ebtel.kaist.ac.kr