Scalable graphene composite membranes for enhanced ion selectivity

Unintended defects are a significant problem for mass production of graphene membranes. Herein, we report a method to fabricate scalable CVD graphene polymer membranes through the formation of a polysulfone (PSf) supporting layer, which is capable of duplicating the Cu morphology. Unintended defects were limited by minimizing defects associated with graphene wrinkles and eliminating polymer residues used in the transfer process. Consequently, the KCl leakage by diffusion of raw graphene membranes fabricated with this method was only ~ 0.5% that of the supporting membrane; there was also no water flux under a pressure of 20 bar. Excellent ion selectivity was achieved by controlling the duration of H2 plasma treatment. The selectivity of KCl over NaCl was 2.61, the selectivity of KCl over MgCl2 was 15.62, and the selectivity of NaCl over MgCl2 was 5.98.