Intercalating ionic liquid in graphene oxide to create efficient and stable anhydrous proton transfer highways for polymer electrolyte membrane

Abstract

Approaches for constructing efficient and stable proton transfer highways in polymer materials are urgently desirable and required for elevated-temperature polymer electrolyte membrane fuel cell (PEMFC). Herein, ionic liquid intercalated GO (IGO) with acceptable fluidity is synthesized by a facile one-pot method and then utilized to construct anhydrous transfer highways in polymer-based composite membrane. The basic-imidazole-cation-containing ionic liquid (IL) increases the flexibility of IGO and meanwhile reinforces the interaction with acidic sulfonated poly(ether ether ketone) (SPEEK) matrix, thus yielding more proportion of perpendicularly oriented IGO and the subsequent formation of 3-D cross-linked IGO networks. The IL molecules act as effective proton carrier sites along IGO networks, and in this way, efficient and long-range transfer highways for “bulk in-plane” proton conduction are constructed. SP-(25I-GO)-10% achieves the maximum conductivity of 7.29 mS cm−1 at 150 °C, 10 times higher than that of SPEEK control membrane. Meanwhile, the maximum current density and power density of SP-(25I-GO)-10% at 90 °C are 574.1 mA cm−2 and 145.1 mW cm−2, increased by 48% and 102% compared with that of SPEEK control membrane, respectively. Additionally, the nanoconfined effect of interlayer renders composite membrane enhanced IL retention ability through capillary force, consequently stable proton conduction and single cell behavior.