Nature celebrates more wonders – potential ones, from flexible armor to affordable fuel cells – that we can make from graphene:
Protons’ ability to travel through graphene suggests that the material could be used as a membrane to sieve hydrogen from air, and to help extract energy from that hydrogen in a fuel cell, says co-author Andre Geim, a materials scientist at the University of Manchester, UK, who won a Nobel prize in 2010 for his pioneering experiments on graphene.
Fuel cells convert the chemical energy stored in hydrogen (or other fuels) into electricity by breaking it apart into protons and electrons: the electrons race around an outside wire to create a current, with the protons flowing through a membrane within the cell. (Electrons and protons recombine at an electrode to react with oxygen.) Today’s membranes, such as a commercial polymer called Nafion, are tens of micrometres thick but do not entirely prevent hydrogen fuel from leaking through; their thickness also means that proton flow is not as great as it might be, reducing the cell’s power. A strong, ultrathin barrier that blocks everything except protons could solve both problems at a stroke.
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Geim’s team used a similar approach to filter clean hydrogen from water using a graphene membrane. Such a technique might pull hydrogen from air, Geim says.
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Graphene has already been proved to be the world’s strongest material — by measuring the resistance of the sheet to being pressed with a diamond tip. But now the material has been targeted by ‘bullets’ for the first time, with tiny silica spheres being fired at layers of graphene.
These layers can very rapidly disperse the energy of an impact before they shatter, because disruptions ripple outward through the material so fast, explains co-author Edwin Thomas, from Rice University in Houston, Texas. The upper limit on this effect is the speed of sound in a material, and in stiff, light graphene, a sound wave can travel at 22 kilometres per second — as opposed to just 332 metres per second in air.