Engineers at the University of Colorado Boulder have produced the first experimental results showing that graphene membranes can effectively and efficiently separate gas molecules.
The findings are claimed to be a significant step toward the realisation of more energy-efficient membranes for natural gas production and for reducing carbon dioxide (CO2) emissions from power plants.
Mechanical engineering professors Scott Bunch and John Pellegrino co-authored a paper in Nature Nanotechnology with graduate students Steven Koenig and Luda Wang detailing the experiments.
According to a statement, the research team introduced nanoscale pores into graphene sheets through ultraviolet light-induced oxidative ‘etching’ and then measured the permeability of various gases across the porous graphene membranes.
Experiments were done with a range of gases including hydrogen, CO2, argon, nitrogen, methane and sulphur hexaflouride — which range in size from 0.29nm to 0.49nm — to demonstrate the potential for separation based on molecular size.
‘These atomically thin, porous graphene membranes represent a new class of ideal molecular sieves, where gas transport occurs through pores which have a thickness and diameter on the atomic scale,’ said Bunch.
Graphene, a single layer of graphite, is said to represent the first truly two-dimensional atomic crystal. It consists of a single layer of carbon atoms chemically bonded in a hexagonal lattice.
‘The mechanical properties of this… material fascinate our group the most,’ Bunch said. ‘It is the thinnest and strongest material in the world, as well as being impermeable to all standard gases.’
Those characteristics make graphene an ideal material for creating a separation membrane because it is durable and yet doesn’t require a lot of energy to push molecules through it, he said.
Other technical challenges will need to be overcome before the technology can be fully realised.
For example, creating large enough sheets of graphene to perform separations on an industrial scale, and developing a process for producing precisely defined nanopores of the required sizes are areas that need further development.