In an alluring twist to what solar cells have been doing so far, Eindhoven University of Technology (TU/e) and FOM Foundation researchers have developed a breakthrough solar cell prototype that produces fuel rather than electricity.
According to the researchers, the Eindhoven-FOM solar cell utilizes gallium phosphide to produce the clean fuel hydrogen gas from liquid water. Processing gallium phosphide in the form of very small nanowires was by itself novel, helping boost the cell’s yield by a factor of ten – all this being done by using a ten thousand times less precious material.
Electricity produced by a solar cell can be used to set off chemical reactions. If this generates a fuel, then be assured, you are looking at the next big thing in alternate energy; solar fuels aren’t just some fancy invention – they are a promising and the best possible replacement for polluting fuels.
According to the researchers, one of the possibilities to speed up this process would be in splitting liquid water using the electricity generated (electrolysis). Among oxygen, this produces hydrogen gas that can be used as a clean fuel in the chemical industry or combusted in fuel cells – in cars for example – to drive engines.
To connect an existing silicon solar cell to a battery that splits the water may well seem an efficient solution now, but the researching community knows for sure that this is going to be a real money-drainer.
Many scientists are therefore targeting their search at a semiconductor material that is able to both convert sunlight into an electrical charge and split the water, all in one; a kind of ‘solar fuel cell.’ Researchers at TU/e and FOM see their dream candidate in gallium phosphide (GaP), a compound of gallium and phosphide that also serves as the basis for specific colored LEDs.
GaP has good electrical properties – its sole drawback being that it cannot easily absorb light when it covers a large flat surface as used in GaP solar cells. Nevertheless, the researchers overcame this problem by making a grid of very small GaP nanowires, measuring five hundred nanometers (a millionth of a millimeter) long and ninety nanometers thick. This immediately boosted the yield of hydrogen by a factor of ten to 2.9 percent – a record for GaP cells till date.
In addition – according to research leader and TU/e professor Erik Bakkers, GaP is also able to extract oxygen from the water, making it possible to design a fuel cell in which you can temporarily store your solar energy.
Image credits: Eindhoven University of Technology