Scientists have discovered a surprising new property of graphene – the world’s thinnest and strongest material – that could accelerate the development of electric cars and other green technologies.
Researchers have found that the newly discovered type of carbon graphite, which is found in pencil lead, allows positively charged hydrogen atoms or protons to pass through it.
Their discovery could increase the efficiency of fuel cells for cars, because the cells generate electricity from hydrogen.
The researchers, led by Nobel Prize winner Sir Andre Geim of Manchester University, who discovered graphene, said their finding raises the possibility that, in future, graphene membranes could be used to ‘sieve’ hydrogen gas from the atmosphere to generate electricity.
This is because the one-atom thick material acts like a filter to allow protons to pass through it, while blocking the passage of other atoms.
The team demonstrated this when they combined the substance with a single-atom material called boron nitride.
Scientists were able collect protons on one side of a membrane, with other blocked atoms accumulated in a chamber.
Using such a membrane, fuel cells could extract hydrogen from the air and burn it in order to power electric cars, which wouldn’t spew out environmentally harmful emissions.
‘We are very excited about this result because it opens a whole new area of promising applications for graphene in clean energy harvesting and hydrogen-based technologies,’ said Marcelo Lozada-Hidalgo, co-researcher on the study.
At just one atom thick, graphene is the thinnest material on Earth and is also 200 times stronger than steel.
It was first isolated in 2004 by Sir Andre and his fellow researchers, who received a Nobel Prize in 2010 for their work.
The material is impermeable to all gases and liquids, giving it the potential for a range of uses such as corrosion-proof coatings, packaging and even super-thin condoms.
The new discovery, published in Nature, came about because the team wanted to investigate whether protons (hydrogen atoms stripped of their electrons) were repelled by the material, which is impermeable to the smallest atom, hydrogen.
They were surprised to find that the protons could pass through the ultra-strong material fairly easily, especially at raised temperatures and if the graphene films were covered with nanoparticles such as platinum, which acted as a catalyst.
Sir Andre and Dr Lozada-Hidalgo hope that graphene could one day be used in proton-conducting membranes, which are a crucial component of fuel cell technology.
Fuel cells, used in some modern cars, use oxygen and hydrogen as fuel and convert the input chemical energy into electricity.
But a major problem is that the fuels leak across the existing proton membranes to reduce the cells' efficiency. This problem could be overcome by using graphene.
The team found that graphene membranes could be used to extract hydrogen from the atmosphere, suggesting the possibility of combining them with fuel cells to make mobile electric generators powered just by tiny amounts of hydrogen in the air.
‘Essentially, you pump your fuel from the atmosphere and get electricity out of it,’ Sir Andre said.
‘Our (study) provides proof that this kind of device is possible.’
Dr Sheng Hu, a postdoctoral researcher and the first author in this work, added: ‘Because graphene can be produced these days in square metre sheets, we hope that it will find its way to commercial fuel cells sooner rather than later’.
SCIENTISTS' REACTIONS TO THE DISCOVERY
Milo Shaffer, Professor of Materials Chemistry and co-director of the London Centre for Nanotechnology at Imperial College London, said: 'The report that protons can penetrate atomically thin layers is both exciting and surprising, especially given that the measured activation energies are significantly lower than predicted by theory.'
Dr Gareth Hinds, Electrochemist specialising in fuel cells of National Physical Laboratory, said: 'While there are challenges to overcome in the manufacture of these 2D layers on a practical scale and questions to be resolved over the mechanism of proton transport, this exciting discovery could have a significant impact on a range of technologies in the energy sector.
'For example, if such a layer could be successfully incorporated between the electrodes of a hydrogen fuel cell, the issue of gas crossover would be completely eliminated, resulting in step changes in power output and stability.
'This would have major implications for an environmentally-friendly technology on the brink of commercialisation.'
