A step closer to sustainable energy from seawater

Credit: greencarcongress.com

That’s the claim, but hydrogen still needs an energy source for its manufacture, so any sustainability depends on what that source is. And looking a bit closer, the report says: “If the extracted hydrogen gas is ultimately used as fuel, for example in a fuel cell of a car, the hydrogen reacts back to water with oxygen gas from the atmosphere.” So what happens when a hydrogen powered fuel cell vehicle trails water from its ‘exhaust’ on to a road in sub-zero temperatures? An icy, or more icy, surface seems likely to be the undesirable result.

The research group led by Leiden chemist Marc Koper has discovered a catalyst that minimizes the production of chlorine gas during salt water electrolysis, reports Phys.org.

The invention can enable the direct production of hydrogen from seawater.

The article has been published in the Journal of the American Chemical Society.

“In the electrolysis of salt water, such as seawater, the ultimate goal is to produce hydrogen at the cathode,” explains Ph.D. student Jan Vos from the Leiden Institute of Chemistry. “The product formed at the anode is ideally oxygen, because that is harmless to the environment.” However, during salt water electrolysis toxic chlorine gas can also form at the anode.

The researchers have now produced a catalyst that minimizes the formation of chlorine gas in favour of oxygen formation. Vos explains: “The catalyst consists of two metal oxides: iridium oxide with a layer of manganese oxide only a dozen nanometers thick. Iridium is a material that exhibits high catalytic activity for the formation of both oxygen gas and chlorine gas; the manganese oxide acts as a kind of membrane that prevents the supply of chloride ions and suppresses the formation of chlorine gas.”

The electrolysis of water is an important step for the production and use of hydrogen as an alternative energy carrier. An anode that counteracts the formation of chlorine gas enables water electrolysis where it is not necessary to first rid the water of dissolved salt, the process of which still costs significant amounts of energy and capital. It would allow the direct production of hydrogen from seawater, thereby relieving the rare freshwater reserves on earth.

According to Vos, a useful side effect of salt water electrolysis is the production of very pure fresh water. “If the extracted hydrogen gas is ultimately used as fuel, for example in a fuel cell of a car, the hydrogen reacts back to water with oxygen gas from the atmosphere. That way, the large-scale application of water electrolysis and hydrogen in fuel cells will lead to large quantities of this ‘waste product’: pure water. In a future where water shortages become an ever more acute problem, this would certainly not be undesirable.”

Continued here.