Zeolitic imidazolate framework decorated on 3D nanofiber network towards superior proton conduction for proton exchange membrane

Abstract

Manipulating membrane nanophase-separation behavior to construct ion-nanochannels for optimizing proton transport was still a challenge. Herein, a novel strategy was proposed for constructing consecutive ion-nanochannels by combining zeolitic imidazolate framework (ZIF-8) and 3D network structure (3DNWS) of poly-m-phenyleneisophthalamide nanofibers (PMIA NFs) via a hydrothermal method. NF hybrid proton exchange membranes (PEMs) were fabricated by filling the inter-fiber voids of 3DNWS-PMIA/ZIF-8 (P/ZIF-8) NFs with Nafion matrix. The structures of P/ZIF-8 and performance of hybrid PEMs were evaluated. The construction of ZIF-8 on 3DNWS-PMIA NFs enabled channels on the basis of the acid–base pair between –SO3H (Nafion) and N–H (imidazole molecule of ZIF-8) to be longer and consecutive. Results showed that P/ZIF-8@Nafion could reach 0.258 S/cm (80 °C, 100% relative humidity) proton conductivity and 150.60 mW/cm2 power density for single-cell performance. In addition, the superiority of 3DNWS of PMIA NFs considerably promoted the thermal and dimensional stability, especially in methanol crossover for hybrid PEMs. This work provided a new approach for preparing high-performance PEMs for direct methanol fuel cells.