Hydrogen fuel produced from sunlight and safely stored

SunlightHydrogen has long been commended as a clean and efficient alternative to gasoline, but so far it hasn’t really been able to live up to expectations. Mostly because it has to be derived from non-renewable sources like coal and natural gas to be cost efficient, but also because it has proven difficult to safely store. Surprisingly two separate research teams have now come up with solutions to both problems.

Splitting water with sunlight

Ideally hydrogen would be produced by splitting water molecules into oxygen and hydrogen. However, currently it takes a tremendous amount of electricity to generate hydrogen that way, making it all but cost efficient. Now scientists from the University of Kentucky and the University of Louisville have found an inexpensive semiconductor material that can split water solely using sunlight as its energy source. Their findings were published in the journal Physical Review B.

Cheap, easy and reusable

Their starting point was taking a cheap and easy-to-produce material and then fine-tuning it to produce the desired results. The alloy they ended up with is 2 per cent antimony, much used in microelectronics, and 98 per cent gallium nitride, a semiconductor that has been in widespread use to make bright-light LEDs.

The alloy functions as a catalyst, meaning that it is not consumed and may be reused indefinitely. When it is immersed in water and exposed to sunlight, the chemical bond between the hydrogen and oxygen molecules in water is broken and hydrogen gas and oxygen are produced.

This makes solar energy into an economically viable, carbon free source for hydrogen, whereas hydrogen production now involves a large amount of CO2-emissions. That means one problem solved one to go: safely storing the hydrogen and of course easily extracting it again after storing.

Safely storing and extracting it

You have probably all heard of the Hindenberg, the zeppelin filled with hydrogen gas that caught fire and exploded in 1937. Now imagine millions of small versions of that explosive potential driving around on the freeway. Not a pleasant idea? Not to worry, because researchers at the University of Southern California (USC) have come up with a way to safely store hydrogen in a harmless chemical material. Their research was published in the Journal of the American Chemical Society.

Binding hydrogen to another chemical material is no challenge (just burning it would create water), but easily and energy efficiently freeing the hydrogen afterwards so that you are able to use it again as an energy source is a whole different story. Earlier this year the USC team already figured out a way to release hydrogen from a harmless chemical material called ammonia borane. Now the scientists have developed a catalysts system to release a sufficient amount of hydrogen from the stable solid material to make is usable as a fuel source.

It seems that there are no more excuses to put off using hydrogen in fuel cells to generate electricity, burning it to produce heat, utilising it in internal-combustion engines to power vehicles or using it in one of the many other scientific or industrial applications.

© Jorn van Dooren | www.bitsofscience.org

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