Ion Transport in Laser-Induced Graphene Cation-Exchange Membrane Hybrids

Abstract

Ion-exchange membranes hybridized with laser-induced graphene (LIG) might lead to membranes with functional surface effects such as antifouling, antibacterial, or joule heating effects; however, understanding the change in the electrical properties of the membrane is essential. Here we studied LIG-modified ion-exchange polymeric membranes using electrochemical impedance spectroscopy (EIS). The conductivity of the anionic sulfonated poly­(ether sulfone) membranes and the effective capacitance of the membrane–electrolyte interface were obtained by fitting the EIS spectra to an electrochemical equivalent circuit and compared with LIG-modified nonionic poly­(ether sulfone) films. The transport selectivity (as the relative permeability) of counterions (K+, Na+, Mg2+, Ca2+) across the membrane was quantified using the membrane’s conductivities obtained from the EIS measurements. The total ohmic resistance of the membrane was directly correlated to the polymer thickness (with negligible contribution from the conductive LIG layer), thereby establishing EIS as a rapid, low-cost, and noninvasive method to accurately probe substrate usage in LIG modification.

Highly Robust Laser-Induced Graphene (LIG) Ultrafiltration Membrane with a Stable Microporous Structure

“…Later, the formation of LIG was studied on a variety of carbon substrates. Graphene made via laser ablation has found niche applications in water purification, , ion transport, energy conversion, electrocatalysis, , and sensors. , Moreover, its thermal conduction, diverse textures, electrical and electrochemical properties, as well as hydrophilicity/hydrophobicity endow LIG with great advantages as antifouling and antibacterial materials. Although laser technology has been applied to a variety of asymmetric microporous membranes, including poly­(ether sulfone) (PES), polysulfone (PSF), and polyphenylsulfone (PPSU), laser irradiation inevitably distorts membrane nanoporous features and therefore limits the application of LIG for application in membranes, where maintaining a robust and interconnected porous structure is important for the separation. , To date, designing and fabricating a mechanically robust LIG membrane has remained an unsolved challenge because laser irradiation distorts the porous structure of the substrate and restricts the use of such materials for filtration.…”

“…Later, the formation of LIG was studied on a variety of carbon substrates. Graphene made via laser ablation has found niche applications in water purification, 6,7 ion transport, 8 energy conversion, 9 electrocatalysis, 10,11 and sensors. 12,13 Moreover, its thermal conduction, 14 diverse textures, 15 electrical and electrochemical properties, 16 as well as hydrophilicity/hydrophobicity 17 endow LIG with great advantages as antifouling 18 and antibacterial 19 materials.…”

Selective Ion Transport through a Self-Standing Protein-Based Biopolymer

“…The membrane resistance ( R i EIS ) was directly obtained from the intercept in the x axis of the Nyquist plot, and subsequently the conductivities (σ i EIS ) of the BSA membrane, fully doped with different metal ions, were calculated using eq . Here, l is the distance between electrodes, and A is the area of the exposed membrane. These conductivities were then used to calculate the mobilities (μ i ; eq ) of the cations and the intercationic transport selectivity ( S i EIS ), i.e., the relative permeability, which ultimately reduces (eq ) to their relative diffusion coefficients where Z i is the charge of the cation, F is the Faraday constant, and C i is the mobile carrier concentration (eq S3), which depends on the water uptake of membrane.…”

“…These conductivities were then used to calculate the mobilities (μ i ; eq 2) of the cations and the intercationic transport selectivity (S i EIS ), i.e., the relative permeability, which ultimately reduces (eq 3) to their relative diffusion coefficients. 26…”

“…The prospects of lignin-, chitin-, chitosan-, and cellulose-based materials for sorption, catalysis, energy harvesting, and storage are well documented. , The selective transport of alkali-metal ions (monoselectivity), although pivotal in biological , as well as water treatment applications, − has never been attempted using these materials. Instead, multiple alternative materials with subnanometer pores, − such as graphene, − carbon nanotubes (CNTs), and metal–organic frameworks (MOFs), ,− have been scouted for this cause. However, for any practical applications, these nanoporous components cannot be used independently and must be combined with some suitable polymer, either in situ synthesized or as mixed-matrix materials. − These multicomponent membranes involve a complex synthesis method and are invariably associated with poor stability (due to component leaching).…”