Graphene Oxide–Polymer Nanocomposite Anion-Exchange Membranes

Abstract

Functionalized graphene oxide (FGO) was incorporated into polyvinyl alcohol/ poly(diallyldimethylammonium chloride) semiinterpenetrating polymer networks (PVA/PDA SIPNs) in order to create novel nanocomposite anion-exchange membranes (AEMs) with improved OH − conductivity and good thermo-mechanical stability at high relative humidity. The nanocomposites were fabricated by a solvent-casting method and subsequently thermally crosslinked to improve their mechanical stability in the hydrated state. The effects of PVA/PDDA ratio, cross-linking method, cross-linking temperature, and FGO content were studied in order to determine the optimal conditions to fabricate AEMs with improved material properties. The membranes were characterized by XRD, FTIR, TGA, FE-SEM, and impedance spectroscopy to assess the material properties of FGO and the nanocomposite membranes. The membranes were also evaluated as polymer electrolytes in anion exchange membrane fuel cells. The results reveal that the membrane fabricated at a PVA/PDDA weight ratio of 70/30 and 20 wt% FGO possesses the highest value of OH − conductivity (12.1 mS cm −1 @ 30 • C and 21 mS cm −1 @ 80 • C), as well as improved thermo-mechanical stability at 100% R.H. However, the fuel cell performance reaches a maximum using the membrane fabricated at 10 wt% FGO. Anion exchange membrane fuel cells (AEMFCs) have attracted considerable attention during the last few years due to some advantages that these kinds of systems offer compared to proton exchange membranes fuel cells (PEMFCs).1,2 For example, thanks to the facile kinetics for electrochemical charge transfer in alkaline environments, it is possible to use less expensive catalysts like nickel and silver in AEM-based fuel cells. 3 In terms of the fuel management, it is also possible to use concentrated fuels to operate these devices, because of the often reduced fuel crossover in AEMs. 4 Unfortunately, AEMFCs have some issues, specifically related to the polyelectrolyte performance. In general, AEMs have lower ionic conductivity than PEMs, mostly due to the fact that conductivity of OH − is intrinsically lower than H + . 5 Another concern with the use of AEMs is the degradation of their cationic groups in strong alkaline media. 6 In addition, AEMs usually exhibit poor solubility in low boiling point and inexpensive solvents, leading to less environmentallyfriendly fabrication processes with high costs and high degree of complexity. 7In order to overcome these limitations, a wide variety of membranes have been proposed during the last few decades as AEMs, including homopolymers, heterogeneous membranes and semi-interpenetrating polymer networks (SIPNs). [8][9][10][11] Among the various options available, SIPNs have gained relevance due to ease of fabrication, acceptable ionic conductivities, and excellent mechanical properties.12-14 More specifically, poly(vinyl alcohol)/poly(diallyldimethylammonium chloride) (PVA/PDDA) SIPNs are promising membranes for applications in electrochemical energy systems mainly because PVA is ...

Composite Anion Exchange Membranes from Quaternized Poly(arylene ether ketone) and Quaternized Titanate Nanotubes with Enhanced Ion Conductivity

“…An important role of an anion exchange membrane is acting as the barrier for the fuels and oxidants between the anode and cathode. According to previous reports, the utilization of inorganic fillers can suppress the fuel/gas permeation due to the increased tortuosity of the transport channels [26,42]. In this work, similar results were also observed for all the obtained nanocomposite QPAEK membranes.…”

“…According to previous reports, the utilization of inorganic fillers can suppress the fuel/gas permeation due to the increased tortuosity of the transport channels [26,42]. According to previous reports, the utilization of inorganic fillers can suppress the fuel/gas permeation due to the increased tortuosity of the transport channels [26,42].…”

“…The pristine QPAEK membrane begun to break in the Fenton's reagent of 30 wt.% H 2 O 2 solution containing 20 ppm FeSO 4 at 30°C after 24 h while completely dissolved 10 days later, while all the QPAEK/QTNT nanocomposite membranes could keep the original integrity after 32 hours and dissolved after 12 days, suggesting the positive effect of the QTNT on enhancing the membrane oxidation endurance. The oxidative stability improvement is very likely attributed to the blocking of penetration of radicals from attacking the polymer skeleton, especially the hydrophilic domains, due to the more compact membrane structure caused by the crosslinking-like function of inorganic nanofillers [26]. The beneficial impact was also found in hydrolytic stability aspect.…”

“…In recent years, significant efforts have been endeavored to using nanomaterials or nanostructures to fabricate nanohybrid polymer electrolyte membranes with high ion conductivity, mechanical properties and physicochemical stability, due to the size-dependent properties including high surface area, tunable size and surface chemistry of the nanomaterials - [19][20][21][22][23][24]. A few kinds of inorganic nanomaterials, for example, silicon dioxide, carbon nanomaterials, metal oxides have been investigated as compositing components for anion exchange membranes [21,[25][26][27][28][29]. For example, quaternized polysulfone and chloromethylated graphene oxides (2 wt.%) nanocomposite membrane exhibited ion conductivity as high as 12.7 mS cm -1 at 60°C and could endure alkali treatment (1 mol L -1 NaOH) for 744 h at 50°C according to Zhang et al's report [27].…”

High Performance of Alkaline Anion-Exchange Membranes Based on Chitosan/Poly (vinyl) Alcohol Doped with Graphene Oxide for the Electrooxidation of Primary Alcohols

“…Recently, carbon nanotubes are incorporated similarly in different polymer structures to enhance their mechanical properties and increase ion conductivities [45][46][47]. GO nanosheets have increased the glass transition (T g ) and electrochemical properties of chitosan biopolymer (CS) [22].…”