Reduced Holey Graphene Oxide Membranes for Desalination with Improved Water Permeance

Reduced-graphene oxide (r-GO) membranes with narrow channels exhibit salt rejections comparable to conventional nanofiltration (NF) membranes. However, their water permeances are much lower because of the high tortuosity for water permeation. Herein we report a facile solution-processable approach to create in-plane nanopores on GO nanosheets before reduction, dramatically decreasing the tortuosity and increasing water permeance while retaining the salt rejection. Specifically, holey GO (HGO) nanosheets were prepared via chemical etching using hydrogen peroxide, followed by the deposition on a porous support by vacuum filtration and then reduction via exposure to hydriodic acid solutions to generate the reduced HGO (r-HGO) membrane. The generation of nanopores increases the water permeance from 0.4 L m^-2∙h^-1∙bar^-1 (LMH/bar) to 6.6 LMH/bar with Na₂SO₄ rejection greater than 98.5 %, and the membranes were robust under strong cross-flow shearing force for 36 h. Both water permeance and Na₂SO₄ rejection of these r-HGO membranes for the first time simultaneously reach the level of the commercial polyamide-based NF membranes. Given their good antibacterial properties and resistance to aggressive chemical washing, the r-HGO membranes show the promise as next-generation NF membranes for desalination.