Nitrile functionalized graphene oxide for highly selective sulfonated poly(arylene ether nitrile)-based proton-conducting membranes

Abstract

4-(3-Aminophenoxy)phthalonitrile grafted graphene oxide (APN-GO) was employed as the filler incorporated into a sulfonated poly(arylene ether nitrile) (SPEN) matrix. The resulting composite membranes show good dispersion and compatibility, which is confirmed through scanning electron microscope. In this process, the existence of hydrogen bonds between amide and sulfonic acid groups can improve the interfacial adhesion and compatibility between the filler and the matrix. Besides, the newly introduced polar nitrile of APN-GO also can increase the intermolecular interaction and make the membranes more compact, which is favorable for the reduction of methanol permeability. Moreover, the composite membranes exhibit improved dimensional stability, proton conductivity and methanol permeability compared to that of a pure SPEN membrane. Furthermore, the composite membrane with 2 wt% filler achieves a high proton conductivity (0.124 S cm⁻¹ at 20 °C and 0.240 S cm⁻¹ at 80 °C) and low methanol permeability (0.117 × 10⁻⁶ cm² s⁻¹ at 20 °C) simultaneously, and exhibits a much higher selectivity (10.598 × 10⁵ S s cm⁻³) than that of Nafion 117 (0.45 × 10⁵ S s cm⁻³). All results indicate the potential of the as-prepared composite membranes for direct methanol fuel cell applications.