Self-Cross-Linked Sulfonated Poly(ether ether ketone) with Pendant Sulfoalkoxy Groups for Proton Exchange Membrane Fuel Cells

Abstract

Among alternative aromatic proton exchange membranes (PEMs) such as the perfluorosulfonic acid one, side-chain-type polymers have drawn great attention due to the formation of hydrophilic and hydrophobic domains and improvement in proton conductivity. In this work, we report the self-cross-linked sulfonated poly­(ether ether ketone) with pendant sulfoalkoxy groups (SPEEK74-O-PAx) prepared by the reaction of hydroxy-functional SPEEK (SPEEK74-OH) with 1,3-propane sultone. The self-cross-linked networks are formed through the electrophilic aromatic substitution reaction catalyzed by protons from the grafted sulfopropyl groups without reducing the sulfonic acid groups. Higher tensile strength, lower water uptake, and in-plane swelling ratio but higher relative water retention than SPEEK74-OH are observed for SPEEK74-O-PAx. The proton conductivity of SPEEK74-O-PA100 is up to 0.1094 S cm–1 at 25 °C, and 0.2003 S cm–1 at 80 °C, which surpasses that of Nafion 212 at each temperature. The introduction of pendant flexible sulfoalkoxy side chains that are favorable for forming distinct steady hydrophilic and hydrophobic domains, and further confirmed by TEM images, can account for the high conductivity. Furthermore, SPEEK74-O-PA100 exhibits the highest power density of 1.358 W cm–2 at a current density of 3.0 A cm–2, which is superior to the performance of Nafion 212 (0.975 W cm–2) and at a high level for aromatic PEMs. The combination of a facile fabrication procedure and remarkable single cell performance enables SPEEK74-O-PAx to be promising membranes for PEM fuel cells.

Preparation of Sulfonated Polytriazoles with a Phosphaphenanthrene Unit via Click Polymerization: Fabrication of Membranes and Properties Thereof

“…The phase-segregated TEM images supported the observations described in AFM. The dark sections referred to the hydrophilic ionic clusters of the sulfonic acid groups, and the bright sections represented the hydrophobic segments of the polymers (Figure g–i). ,, In the case of PTDPBSH-70 (Figure g), a good phase-separated morphology was observed, where the density and the size of the hydrophilic ionic domains were low. The density and the size of the ionic clusters were amplified in PTDPBSH-80 (Figure h) and PTDPBSH-90 (Figure i), along with a more distinct and interconnecting ionic nanocluster-like morphology.…”

Constructing Proton Transfer Channels Using CuO Nanowires and Nanoparticles as Porogens in High-Temperature Proton Exchange Membranes

“…Sufficient tensile strength is necessary for HTPEMs. It is an effective method to enhance the dimensional stabilities and tensile strength of the membranes at the high-temperature condition by covalent cross-linking. ,− The membranes’ mechanical properties were characterized before and after PA doping. Figure a,c show the tensile curves of membranes before PA doping.…”

Highly proton conductive and stable sulfonated poly(arylene-alkane) for fuel cells with performance over 2.46 W cm−2

“…Commercially available PFSA membranes such as Naon membranes have been the benchmark over the last few decades because of their outstanding proton conductivity, mechanical properties, desired oxidative stability, etc. 1,2 Nevertheless, the high cost, environmental harm, gas crossover and complex preparation processes prevent their large-scale commercialization. 3 Hence, it has become a new focus to prepare low-cost hydrocarbon-based PEMs.…”