Researchers at the University of Manchester, in UK, have discovered a new property to add to the long list of uses of graphene. The study, led by Nobel Laureate Andre Geim, debunks the previously-held belief that one-atom thick substances like graphene and hexagonal boron nitride( hGN) are impermeable. Based on the research, the scientists have concluded that such materials allow protons to pass through them; a breakthrough that will likely lead to more efficient fuel cells as well as electric generators capable of extracting usable hydrogen directly from the atmosphere.
Graphene, as some might already know, is a multi-functional monolayer of pure carbon, first isolated and studied in 2004 by a group of University of Manchester researchers. Known for its remarkable strength and high electrical conductivity, graphene was so far believed to be impermeable to all known gases and fluids. A single atom of hydrogen would take billions of years to penetrate the material. This feature has led to the use of graphene in the production of impervious packaging and gas separation membranes.
However the research, published in Nature journal, shows that super-thin substances, like graphene and boron nitride, allow an easy passage of protons, as in hydrogen atoms minus their electrons. The proton-conducting property of these materials gets heightened at higher temperatures and also, when covered with nanoparticles of catalysts such as platinum. One of the major applications of the discovery is with regard to proton exchange membranes(PEM). PEMs form the basis of modern fuel cells, in which the chemical energy of the reactants, oxygen and hydrogen, gets converted into electricity. Central to the fuel cells are membranes that are impervious to everything, except for protons.
Scientists believe that the PEM fuel cells would likely replace the internal combustion engine, of vehicles, in the future. One of the chief obstacles, in the case of proton-conducting membranes, is fuel crossover, that decreases their durability and efficiency. According to the latest research, one-atom-thick layer of graphene and hBN can provide thinner membranes, that can effectively lower fuel crossover and cell poisoning, thus leading to greater efficiency. The researchers believe that further development of such PEM technology will make hydrogen a feasible alternative to the conventional fossil fuels.
Additionally, the study has shown that this new property of graphene could help extract hydrogen from air, especially humid atmosphere. A zero-pollution fuel, hydrogen is high in energy. The research has opened doors to a number of possibilities, including advanced mobile electric generators, that are powered by hydrogen extracted from the surrounding atmosphere. PhD student and co-author of the paper, Marcelo Lozada-Hidalgo said:
When you know how it should work, it is a very simple setup. You put a hydrogen-containing gas on one side, apply small electric current and collect pure hydrogen on the other side. This hydrogen can then be burned in a fuel cell…We worked with small membranes, and the achieved flow of hydrogen is of course tiny so far. But this is the initial stage of discovery and the paper is to make experts aware of the existing prospects. To build up and test hydrogen harvesters will require much further effort.
Talking about the project, first author Dr. Sheng Hu said:
It looks extremely simple and equally promising. 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.