Dramatic Improvement in Water Retention and Proton Conductivity in Electrically Aligned Functionalized CNT/SPEEK Nanohybrid PEM

Abstract

Nanohybrid membranes of electrically aligned functionalized carbon nanotube f CNT with sulfonated poly ether ether ketone (SPEEK) have been successfully prepared by solution casting. Functionalization of CNTs was done through a carboxylation and sulfonation route. Further, a constant electric field (500 V·cm(-2)) has been applied to align CNTs in the same direction during the membrane drying process. All the membranes are characterized chemically, thermally, and mechanically by the means of FTIR, DSC, DMA, UTM, SEM, TEM, and AFM techniques. Intermolecular interactions between the components in hybrid membranes are established by FTIR. Physicochemical measurements were done to analyze membrane stability. Membranes are evaluated for proton conductivity (30-90 °C) and methanol crossover resistance to reveal their potential for direct methanol fuel cell application. Incorporation of f CNT reasonably increases the ion-exchange capacity, water retention, and proton conductivity while it reduces the methanol permeability. The maximum proton conductivity has been found in the S-sCNT-5 nanohybrid PEM with higher methanol crossover resistance. The prepared membranes can be also used for electrode material for fuel cells and batteries.

Sulfonated graphene oxide/Nafion composite membranes for high temperature and low humidity proton exchange membrane fuel cells

“…36 A piece of membrane (30 mm  5 mm) was placed across the Pt probes, and membrane resistance (R, U) was measured using a Keithley Electrometer as a function of applied voltage. The electrical conductivity (s) of membrane specimens can be calculated using the eqn (8):…”

Toward improved mechanical strength, oxidative stability and proton conductivity of an aligned quadratic hybrid (SPEEK/FPAPB/Fe3O4-FGO) membrane for application in high temperature and low humidity fuel cells

“…A piece of dry specimen (30 mm  5 mm) was placed across the Pt electrodes and current was measured as a function of applied voltage, as described in the literature. 33 The following equation was used to calculate the electrical conductivity (s) of membrane specimens.…”

“…In general, two types of water are available in the PEM: (i) covalently bound hydrophilic functionalities named as bound water and (ii) non-covalently bound hydrophilic moieties named as free water. 33 Bound water is mostly contributed to proton conductivity of PEM rather than free water. The % of bound water content in prepared membranes was calculated from TGA curves (100-230 C), and the values are shown in Table 2.…”

“…The aligned hybrid membrane exhibited signicant improvements in mechanical properties due to high tensile stiffness of vertically aligned F-CNTs when compared to randomly aligned F-CNTs. 33 Beydaghi et al incorporated and subsequently aligned the Fe 3 O 4 -FGO into the PVA matrix using a constant magnetic eld (0.25 T). With aligned Fe 3 O 4 -FGO, the proton conductivity of composite membrane increases by 1.1 folds, due to the wide and regular proton conduction paths.…”

Sulfonated fullerene in SPEEK matrix and its impact on the membrane electrolyte properties in direct methanol fuel cells

“…Apart from the studies related to graphene, CNTs are also explored as suitable additive for SPEEK to study its mechanical and electrochemical properties. Swati Gahlot et al prepared the composite membranes of SPEEK with electrically aligned functionalized CNTs and studied the physico-chemical characteristics of composite membranes [29]. It is noteworthy that our earlier reports on the preparation of composite membranes of SPEEK and PSSA functionalized…”