Construction of Interpenetrating Transport Channels and Compatible Interfaces via a Zeolitic Imidazolate Framework “Bridge” for Nanofibrous Hybrid PEMs with Enhanced Proton Conduction and Methanol Resistance
Liyuan Wang, Nanping Deng, Gang Wang, Jingge Ju, Meng Wang, Bowen Cheng, Weimin Kang
Abstract
A novel three-dimensional sulfonated poly(ether sulfone) (SPES) nanofiber@ZIF-8 network (ZSNF) with an interlaced structure was designed and prepared by an in situ assembling zeolitic imidazolate framework-8 (ZIF-8) shell on electrospun SPES nanofiber surfaces. By incorporating ZSNFs into the Nafion matrix, highly compatible interfaces were well constructed via the interfacial Hmim···–SO3H pairs between the interaction of the highly ordered ZIF-8 nanoparticles to the SPES nanofibers and the Nafion matrix in the hybrid membranes. Moreover, the Hmim···–SO3H pairs along the interfaces (the interface between SPES nanofibers and ZIF-8 and the interface between ZIF-8 and the Nafion matrix) could generate additional proton acceptors and donors to facilitate proton conduction or hopping via vehicle and Grotthuss mechanisms. In addition, the well-interconnected network structure of SPES@ZIF-8 nanofibers might promote the formed proton conducting channels with good interconnectivity, leading to interpenetrating transport channels to further speed up the diffusion and conduction of protons. Benefiting from the physicochemical and structural synergy advantages of ZSNFs with the Nafion matrix, the Nafion/ZSNF hybrid membranes presented a highly elevated proton conductivity of 0.265 S cm–1 at 80 °C with high humidity. Additionally, the anhydrous proton conductivity also reached 4.78 × 10–3 S cm–1 at 120 °C, which was much higher when compared to that of the recast Nafion membrane (2.57 × 10–3 S cm–1). The methanol blocking ability and mechanical stability of Nafion/ZSNF hybrid membranes were simultaneously enhanced because of the interconnected network structure of ZSNFs as well as the tight interactions and high compatibility between the interfaces, which endowed the Nafion/ZSNF hybrid proton-exchange membrane with an outstanding single-cell performance with a peak power density of 116.50 mW cm–2 (182.4% higher than that of Nafion 117).