Imperfect Graphene Could Lead to Better Fuel Cells, Water Filters
A group of scientists headed by Dr Franz Geiger of Northwestern University has found that slightly imperfect graphene shuttles protons, and only protons, from one side of the graphene membrane to the other in mere seconds. The membrane’s speed and selectivity are much better than that of conventional membranes, offering researchers a new and simpler mechanism for design of fuel cells, water filtering and desalination membranes.
Proton transfer channel across a quad-defect in graphene. Image credit: Murali Raju / Penn State.
“Imagine an electric car that charges in the same time it takes to fill a car with gas,” said Dr Geiger, who is the senior author of the paper published in the journal Nature Communications .
“And better yet – imagine an electric car that uses hydrogen as fuel, not fossil fuels or ethanol, and not electricity from the power grid, to charge a battery.”
“Our surprising discovery provides an electrochemical mechanism that could make these things possible one day.”
In their study, Dr Geiger and his colleagues tested the possibility of using graphene as a separation membrane in water
While many scientists strive to make graphene defect-free to exploit its superior electronic properties, Dr Geiger’ team found that graphene required the vacancies to create water channels through the membrane.
Computer simulations showed the protons were shuttled across the barrier via hydroxyl-terminated atomic defects, that is, by oxygen hydrogen groups linked at the defect.
“Our simulations and experiments showed that you need to have at least four carbon vacancies and some sort of channel to overcome the energy barrier that would normally prevent the protons from crossing to the other side,” said study co-author Dr Adri van Duin of Pennsylvania State University.
“If we can learn how to engineer the defects and the defect size, we could make an effective separation membrane.”
“Although it still requires a lot of design work, clearly this looks highly attractive for many applications, including desalinization.”
“It may also work for a new, less complicated design for fuel cells in the future,” Dr Geiger said.
“Our results will not make a fuel cell tomorrow, but it provides a mechanism for engineers to design a proton separation membrane that is far less complicated than what people had thought before.”
“All you need is slightly imperfect single-layer graphene.”