Flocculating-filtration-processed mesoporous structure in laminar ion-selective membrane for osmosis energy conversion and desalination

Ion-selective membrane based technologies, such as electrodialysis and reverse electrodialysis technology, show great potential in addressing challenge of the water-energy nexus. However, the ion-selective membrane usually suffers from the trade-off between ionic selectivity and ion transport capacity. Here, we prove that mesoporous structure in lamellar ion-selective membrane can increase the transmembrane ionic transport with no loss of ionic selectivity. The mesoporous structure is constructed via adjusting the pH of graphene oxide/ionic polymer solution and self-assembly of flocculating solution. Negatively or positively charged graphene oxide based membrane with a thickness of 4 μm was used in a three-compartment electrochemical cell for osmosis energy conversion and desalination. An output power density of 5.87 W m−2 is achieved by mixing artificial seawater (0.5 M NaCl) and river water (0.01 M NaCl). The conductivity of seawater can quickly decrease from 12.3 mS cm−1 to 36 μS cm−1 in typical electrodialysis process, showing the excellent desalination ability. This work proves a new strategy of enhancing transmembrane ionic transport in ion-selective membrane and provides new opportunities for 2D nanomaterials.