Enhanced proton conductivity of SPEEK membranes by constructing hydrogen bond network through doping ionic liquid and graphene oxide

Abstract

So as to improve proton conductivity at medium temperatures while reducing the loss of ionic liquids (ILs), this article fabricated a series of hybrid membranes with sulfonated poly (ether ether ketone) (SPEEK) as their base material, 1‐allyl‐3‐methylimidazolium chloride ([AMIM][Cl]) as their primary proton conductor, and graphene oxide (GO) as their filler. The characterization results showed that the –SO3H groups of SPEEK formed acid–base pairs with the imidazole ring of [AMIM][Cl] at the interface where electrostatic attraction inhibited the main‐chain migration of the SPEEK. At the same time, the large hydrogen bond network formed between [AMIM][Cl], GO and SPEEK provided more jump sites for proton transfer. Proton conduction of the prepared membranes was enhanced by way of low potential energy barriers. At 120°C, SPEEK/IL/GO‐2% exhibited a proton conductivity of 21.35 mS/cm, and the IL loss rate was 20.17%. The characterization results demonstrated that the prepared SPEEK/IL/GO composite membranes had excellent physicochemical properties, dimensional stability, high proton conductivity, and low IL loss, which were expected to be used in practical conditions at medium temperature.Highlights Large hydrogen bonding network provides additional proton hopping sites. Physical cross‐linking limits the leaching of ionic liquid. SPEEK/IL/GO‐2% membrane achieves a conductivity of 21.35 mS/cm at 120°C.