Facile Fabrication of Graphene Membranes with Readily Tunable Structures

Abstract

Advanced membranes that combine mechanical robustness with fast permeation are crucial to many applications such as water purification, ions selectivity, and gas separation. Graphene sheets offer a promising opportunity to fabricate thin, high-flux, and pressure-endurable membranes because of their unique 2D morphology, oxidizable surface, and electrical conductivity. We herein report a highly effective yet simple approach to the fabrication of graphene membranes featuring controllable oxidation degrees and thus tunable structures and properties. The graphene sheets comprise a single or a few layers with a lateral dimension of 50-100 nm; their C/O ratios can be manipulated from 4.1 for graphene with a low degree of oxidation (low-oxidation graphene) to 2.5 for medium-oxidation graphene to 1.3 for high-oxidation graphene, by controlling the proportion of phosphoric acid during the 60 min fabrication. Fabricated by simple vacuum filtration, the membranes exhibited various water flux from 200.0 to 20.0 L/m(2)·h·bar at 3 bar of pressure and mechanical robustness (Young's modulus can be up to 20 GPa and tensile strength to 100 MPa). When these membranes were used as electrodes for supercapacitors, specific capacitances of 58.8 F/g and 23.5 F/cm(3) were recorded for the low-oxidation graphene membrane at 1 A/g by a two-electrode configuration; the capacity values retained ∼95% after 800 cycles; the high capacitance would be caused by moderate wettability and high electrical conductivity.

Graphene Platelets and Their Polymer Composites: Fabrication, Structure, Properties, and Applications

“…GnPs were produced by a chemical intercalation and exfoliation method, and then they were deposited through vacuum filtration. During filtration, platelets were aligned perpendicular to the flow direction, resulting in a rough membrane full of various pores . Since the membranes are flexible (Figure c 2 ), porous (Figure c 3 ), and conductive, the electrodes are able to: (i) accommodate the volumetric expansion of sulfur during lithiation, (ii) store and reuse migrating polysulfides, and (iii) provide low charge transfer resistance 52.6 Ω .…”

Non‐oxidized graphene/elastomer composite films for wearable strain and pressure sensors with ultra‐high flexibility and sensitivity

“…More attention has been turned to graphene due to its excellent electrical conductivity (6000 S/cm) and exceptional mechanical properties (Young's modulus 1 TPa, tensile strength 130 GPa, stretch‐ability 0%~25%) . However, independent of the chemical modification of graphene sheets, they have less electrical conductivity and less strength due to their relatively high defect concentration . These properties may cause negative effect on the performance of strain sensors .…”

Synthesis of graphene oxide membranes and their behavior in water and isopropanol

“…Furthermore, interactions of solvents with GO and their role in determining the permeability through GO membranes is also critical for solvent based applications [31]. Shi et al observed a decrease in permeation of water while increasing oxidation extent of the GO, likely due to a higher degree of hydrogen bonding [32]. Water can form a stable adsorbates on the GO surface which has been observed to narrow the capillaries for flow of the fluids.…”