Potential role for graphene membranes in natural gas production
11 October 2012
Researchers have shown that atomically thin graphene membranes with tiny pores can effectively and efficiently separate gas molecules through size-selective sieving.
Illustration courtesy of Zhangmin Huang
The findings, by Engineering faculty and students at the University of Colorado Boulder, are a significant step toward the realisation of more energy-efficient membranes for natural gas production and for reducing carbon dioxide emissions from power plant flues.
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, carbon dioxide, argon, nitrogen, methane and sulphur hexafluoride - ranging in size from 0.29 to 0.49 nanometers - to demonstrate the potential for separation based on molecular size.
The characteristics of graphene make it 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.
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. The UoC-Boulder experiments were done on a relatively small scale.
The illustration above depicts a single molecular-sized pore in a graphene membrane. The membrane is separating carbon dioxide from nitrogen. A carbon dioxide molecule is passing through the pore while nitrogen molecules are too large to pass through.