Abstract
An effective strategy to improve both the conductivity and alkaline stability of anion exchange membranes (AEMs) was proposed by incorporating imidazolium ionic liquids (ImILs) modified 1D carbon nanotubes (IL@CNT) into imidazolium-based poly (ether ether ketone) (ImPEEK). Two types of ionic liquids (IL-M and IL-B) with different alkaline stability were chemically attached to CNTs. The introduction of IL@CNT provided the hybrid membranes with additional ion hopping positions and 1D long-range ion-conducting channels. The ImPEEK/IL-B@CNT-6 membrane with a high ion exchange capacity (IEC) of 2.49 mmol g(-1) possessed the hydroxide conductivity of 134.52 mS cm(-1) (70 degrees C, 100% RH) which was 1.7 times that of the pure ImPEEK membrane (80.20 mS cm(-1)). Meanwhile, the hybrid membranes showed enhanced alkaline stability due to the steric hindrance offered by CNTs and good alkaline resistance of IL-B with more bulky substituents. The residual ratio of hydroxide conductivity of ImPEEK/IL-B@CNT-8 after being treated in 2 M KOH at 50 degrees C for 48 h reached 77.47% (54.37% for pure ImPEEK and 70.21% for ImPEEK/ILM@CNT-8). The theoretical calculations of LUMO energy for IL-M (-1.83 eV) and IL-B (-1.74 eV) were in good accordance with experimental results. The ImPEEK/IL-B@CNT-6 hybrid membrane presented an improved fuel cell performance with the peak power density of 80.59 mW cm(-2) at 50 degrees C which was 1.6 times that of the pure ImPEEK membrane. Mechanical properties, dimensional and thermal stability of the as-prepared hybrid membranes were also enhanced due to the improved interface compatibility.