Multifunctional coatings of graphene oxide: New membranes for proton permeation and salt rejection

We report the surface modification of nanochannels whose channels are formed from stacked and overlapping graphene oxide sheets, in which the high density of nitrogen/oxygen groups and networks of H bonds serve as excellent proton channels but block the transport of cations such as Li+ and Na+. The membrane has excellent stability when immersed for long periods under water and has an NaCl rejection rate of approximately 99% while maintaining permeability to water and performs well for at least 400 h for desalination. Our straightforward approach to achieving this type of two-dimensional channel material for selective ion conduction, efficient ion separation, and water desalination might open a host of possible new uses.