Temperature Dependence of the Pore Structure in Polyvinylidene Fluoride (PVDF)/Graphene Composite Membrane Probed by Electrochemical Impedance Spectroscopy

Abstract

In this paper, graphene was introduced in the PVDF to improve the thermal stability of the pore structure, which is the key feature for the membrane applied for the thermo-osmotic energy conversion (TOEC) process. The PVDF/graphene composite membranes were characterized by a scanning electron microscopy (SEM), a water contact angle measurement, and electrochemical impedance spectroscopy (EIS). It was found that the composite membranes exhibited improved surface hydrophobicity. Moreover, the pores in pure PVDF membrane would expand during the heat process while the existence of graphene in PVDF clearly suppressed the expansion, which implied better thermal stability of the pores in the composite membrane. According to the pore deformation time, the heat conductivities of the membranes were calculated and compared with each other. It confirmed that the composite membrane with higher graphene content exhibited enhanced heat conductivity. EIS can be used to monitor the temperature dependence of the pore structure in aqueous environments.

Property Characterization and Mechanism Analysis of Polyoxometalates-Functionalized PVDF Membranes by Electrochemical Impedance Spectroscopy

“…Therefore, the observation of GO membrane morphology by SEM, TEM, and AFM, which are typically operated in a vacuum environment, can hardly establish the correlation between the membrane structure and membrane performances. Other techniques, for example, electrochemical impedance microscopy (EIS) [ 9 ], has showed its advantage in providing more information of the membrane structures in such cases.…”

“…Electrochemical impedance spectroscopy (EIS), as an economic and non-invasive characterization technique, can be potentially utilized to study the membrane structures [ 9 , 17 , 18 ], membrane fouling [ 19 , 20 ], and internal concentration polarization (ICP) [ 21 ]. The electrochemical relaxations are related to the intrinsic properties of the studied systems; thus, it can reveal structural features such as structural layers, pore structures, etc., through suitable equivalent circuit modeling.…”

“…Compared with other traditional structural characterization methods, EIS can provide deeper and more considerable information of membrane structures. For instance, Luo and co-workers used EIS to probe the effect of the graphene integrated into the polyvinylidene fluoride (PVDF) membrane matrix on the thermal stability, illuminating that the introduction of graphene improved the membrane stability and suppressed thermal expansion of the pore structures [ 9 ]. In addition, EIS also successfully demonstrated that montmorillonite, as a typical two-dimensional (2D) material, adjusted the pore structures of ethyl cellulose membranes, resulting in two different kinds of pores in the composite membranes [ 28 ].…”

Glucose/Graphene-Based Aerogels for Gas Adsorption and Electric Double Layer Capacitors

“…Macroscopic three-dimensional (3D) graphene structures have been obtained by interconnecting 2D graphene sheets that have been successfully synthesized via various methods. In addition to the inherent properties of 2D graphene, 3D graphene structures present large accessible surface areas, excellent mechanical strength and great flexibility because of their porous interconnected network structures [1,2,3,4]. Therefore, 3D graphene is widely studied in the gas adsorption and supercapacitor fields.…”

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

“…Electrochemical impedance spectroscopy (EIS) is a noninvasive tool that is extensively used to study the chemical, electrochemical, interfacial structural, as well as ion-transport properties of different types of membranes. ,− This alternating-current-based technique allows the differentiation between the individual contributions of different phenomena occurring at the membrane surface and not accessible by direct-current-based measurements . Published EIS studies on graphene–polymer hybrids are scarce, and the EIS of 3D LIG has not yet been reported. Here we incorporated LIG on synthesized (see the SI) ion-exchangeable membranes (sulfonated poly­(ether sulfone) (SPES)) or nonporous nonionexchangeable membranes (poly­(ether sulfone) (PES)) and used EIS to explore the electrical properties of the hybrid membranes (SPES–LIG or PES–LIG) during cation (Na + , K + , Mg 2+ , Ca 2+ ) transport.…”