Ion selectivity of graphene nanopores.
As population growth continues to outpace development of water infrastructure in many countries, desalination (the removal of salts from seawater) at high energy efficiency will likely become a vital source of fresh water. Due to its atomic thinness combined with its mechanical strength, porous graphene may be particularly well-suited for electrodialysis desalination, in which ions are removed under an electric field via ion-selective pores. Here, we show that single graphene nanopores preferentially permit the passage of K(+) cations over Cl(-) anions with selectivity ratios of over 100 and conduct monovalent cations up to 5 times more rapidly than divalent cations. Surprisingly, the observed K(+)/Cl(-) selectivity persists in pores even as large as about 20 nm in diameter, suggesting that high throughput, highly selective graphene electrodialysis membranes can be fabricated without the need for subnanometer control over pore size.
Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
Ryan C
RC
Rollings
School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
Aaron T
AT
Kuan
Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.|School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
Jene A
JA
Golovchenko
D000838:Anions / Q000302:isolation & purification*; D002413:Cations, Divalent / Q000302:isolation & purification*; D002414:Cations, Monovalent / Q000302:isolation & purification*; D003956:Dialysis; D060766:Drinking Water / Q000737:chemistry; D055664:Electrochemical Techniques; D006108:Graphite / Q000737:chemistry*; D006801:Humans; D007474:Ion Exchange; D007700:Kinetics; D008567:Membranes, Artificial; D016062:Porosity; D054712:Salinity; D012623:Seawater / Q000737:chemistry*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
D000838:Anions; D002413:Cations, Divalent; D002414:Cations, Monovalent; D060766:Drinking Water; D008567:Membranes, Artificial; D006108:Graphite