One-pot simultaneous ARGET ATRP strategy on widening long-range ion channels to facilitate ion conductivity for alkaline anion exchange membrane fuel cells

Abstract

Here, we report a new facile method to improve both the conductivity and alkaline stability of anion exchange membranes (AEMs) by directly growing poly(ionic liquid) (imidazolium cations, PImIL) from bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide) (BrPPO) and the surface of bromobenzylated carbon nanotubes (Br@CNTs) via one-pot simultaneous activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) and the following ionizing co-crosslink. Both PPO and CNTs are deeply ionized to fabricate a kind of dual-cation organic–inorganic hybrid co-crosslinked network with widening long-range ion transport channels in AEMs, which endows the resultant hybrid membrane with excellent ion conductivity, dimensional stability, and mechanical strength. The PPO-PImIL/PImIL@CNT hybrid co-crosslinked membrane with a higher ion exchange capacity of 2.29 mmol g⁻¹ shows a hydroxide ion conductivity of 189.8 mS cm⁻¹ at 80 °C, about 2.5 times higher than that of pristine imidazolium-modified PPO (ImPPO). Meanwhile, the alkaline stability of the membrane is enhanced due to the steric hindrance offered by CNTs, hydrophobic alkyl chain spacers for cationic functional groups, and the hybrid co-crosslinked network. The optimized interfacial compatibility between PPO-PImIL and PImIL@CNTs also endows the hybrid membranes with considerable tensile strength (26.7 MPa, almost 250% of the pristineImPPO) and thermal stability (higher than 200 °C). The hybrid co-crosslinked AEM (4 wt% of Br@CNTs relative to BrPPO was used) presents an outstanding fuel cell performance with a maximum power density of about 446 mW cm⁻² and good durability of the single cell (0.76 mV h⁻¹ of voltage decay rate). The excellent overall performance renders hybrid co-crosslinked AEMs a potential candidate for application in AEMFCs.