Constructing Continuous Proton-Conducting Highways within Sulfonated Poly(Arylene Ether Nitrile) Composite Membrane by Incorporating Amino-Sulfo-Bifunctionalized GO

To obtain a proton exchange membrane (PEM) with high proton conductivity and low methanol permeability, a novel amino-sulfo-bifunctionalized GO (NSGO) was synthesized and explored as a filler for sulfonated poly(arylene ether nitrile) (SPEN). The result indicated that the microstructure of composite membranes was rearranged by NSGO and strong acid–base interactions were formed between fillers and the SPEN matrix, affording enhanced thermal, mechanical, and dimensional stabilities. Moreover, it was found that NSGO fillers were uniformly dispersed in the SPEN matrix, generating efficient proton-conducting paths along the SPEN/NSGO interface. Meanwhile, the sulfonic and amino groups of NSGO served as additional proton hopping sites to connect the ionic clusters in the SPEN matrix, creating interconnected and long-range ionic pathways. In such a way, proton-conducting highways with low energy barriers are constructed, which enhance the proton conductivity of the composite membranes via the Grotthuss mechanism. Furthermore, the composite membranes also effectively prevent methanol permeation, and therefore high selectivity (the ratio of proton conductivity and methanol permeability) is endowed. Compared to SPEN membrane, a 3.6-fold increase in selectivity is obtained for the optimal composite membrane. This study will provide a new strategy for the preparation of high-performance PEM.