Polyoxometalate-polymer nanocomposites with multiplex proton transport channels for high-performance proton exchange membranes

Multiplex ion channels play a critical role in life processes and are highly desired for advanced electrolytes due to the synergistic effect on ion transport. However, it is a challenge to integrate different types of proton transport channels in the same membrane system while keeping their intrinsic structural stability. Here, we report a facile strategy for the preparation of nanostructured polymer composite membranes with multiplex proton transport channels based on the supramolecular co-assembly of sulfonated poly(ether-ether-ketone) (SPEEK), poly(ether-ether-ketone)-grafted-poly(vinyl pyrrolidone) (PGP) and polyoxometalate H3PW12O40 (PW). The spherical ionic domains from SPEEK and the bicontinuous ionic domains from the electrostatically assembled PGP/PW components were fabricated in the membranes simultaneously, which co-construct the multiplex channels for proton conduction. The optimized membranes exhibit a high proton conductivity of ∼130 mS/cm and a high modulus of ∼4.3 GPa, which are ∼2.2 and ∼1.3 times higher than the pristine SPEEK, respectively. Furthermore, the direct methanol fuel cell performance based on these membranes is enhanced by 50.4% compared to SPEEK. This approach can provide a paradigm to design advanced polymer electrolyte membranes with highly efficient ion-conducting channels for energy applications.