Ion Transport through Perforated Graphene

Abstract

We investigated the dependence of ion transport through perforated graphene on the concentrations of the working ionic solutions. We performed our measurements using three salt solutions, namely, KCl, LiCl, and K2SO4. At low concentrations, we observed a high membrane potential for each solution while for higher concentrations we found three different potentials corresponding to the respective diffusion potentials. We demonstrate that our graphene membrane, which has only a single layer of atoms, showed a very similar trend in membrane potential as compared to dense ion-exchange membranes with finite width. The behavior is well explained by Teorell, Meyer, and Sievers (TMS) theory, which is based on the Nernst–Planck equation and electroneutrality in the membrane. The slight overprediction of the theoretical Donnan potential can arise due to possible nonidealities and surface charge regulation effects.

Graphene Membranes: Transport Properties and Energy Applications

“…A variety of techniques can be used to create nanopores in graphene. This includes methods such as drilling pores through a focused ion [4][5][6][7][8][9][10] or electron beam [11][12][13], etching [14][15][16] chemical activation [17][18][19][20][21] and electrical pulses [22]. Focused ion beam (FIB) drilling is one of the most commonly used techniques to create porous graphene, [7,23] as it allows the formation of pores with broad diameters ranging from 10 nm to 1 µm [7,15,24,25].…”

“…Basically, in this method a beam of ions, such as Ga [4,[6][7][8][9], Ar, [5] He [7,26] or Xe [10] ions, is used to bombard a selected graphene area (nm 2 ), sputtering carbon atoms from the surface and leaving holes behind. The shape, and dimensions of the created holes and pore density are affected by the ion diameter and ion type (larger dimeter creates larger pores), exposure time, and energy level of the ion beam (electron volt).…”

“…Interestingly it has been found that by increasing the oxygen plasma exposure time, the treated graphene switches from a proton transport membrane to a proton and ion transport membrane, whereas for the argon plasma treatment, only protons are allowed to transport [15]. The oxygen plasma etching time not only increases the defect density but also enlarges the defects in graphene, whereas for argon plasma, extending the etching time only increases the density of the defects [15] Etching can also be achieved through NaOH solutions or via UVoxidative etching [10,16]. Another top-down approach to generate NPG membranes is chemical activation, which involves the use of various chemicals e.g., KOH to remove carbon atoms.…”

Single-layer graphene as a highly selective barrier for vanadium crossover with high proton selectivity

“…Recent experimental findings have established exclusive high proton transmission through single-layer graphene (ca. 0.5-0.78 eV [34,35], energy barrier) while simultaneously blocking transmission of other species [36][37][38][39]. It has been reported that the graphene sheets consisted of interatomic openings in their electron density distribution (ca.…”

Selective ion sieving through arrays of sub-nanometer nanopores in chemically tunable 2D carbon membranes

“…Ion selectivity in transport through the membrane pores is based on electrostatic repulsion by charges present on the membrane surface, as shown by a range of studies probing charge-selective ion transport through nanoporous 2D membranes. [17][18][19] In the BPT-CNM, charged groups include residual sulfide groups. 20 Moreover, ion selectivity in 2D nanoporous membranes has been observed even in chemically neutral membranes, including graphene and molybdenum sulfide.…”