Construction of three-dimensional proton-conduction networks with functionalized PU@PAN/UiO-66 nanofibers for proton exchange membranes.

[Display omitted] • A strategy for MOF-composite nanofiber with synergistic architecture is proposed. • PU@PAN/UiO-66 core/shell nanofiber is prepared by coaxial electrospinning. • 3D proton-conduction networks are constructed in proton exchange membrane. • Sulfamic acid is successfully introduced on nanofiber. • The maximum power density of Nafion/S@NF-50 exhibits 182.6 mW cm−2. Proton exchange membranes (PEMs) play an important role in fuel cells. For realizing a nanofiber (NF) structure design in PEMs, the material should have tunable pores and a high specific area. In this study, we attempt to design a novel NF with synergistic architecture doped MOF for constructing three-dimensional (3D) proton conduction networks in PEMs. In this framework, UiO-66-COOH serves as a platform for proton sites to synergistically promote proton conductivity via polyvinylpyrrolidone dissolution, hydrolyzation of polyacrylonitrile, and sulfamic acid functionalization of the shell-layer NF. Benefiting from enriched proton-transfer sites in NFs, the obtained composite membrane overcomes the trade-off among proton conductivity, methanol permeability, and mechanical stability. The composite membrane with 50 % fiber (Nafion/S@NF-50) exhibited a high proton conductivity of 0.212 S cm−1 at 80 °C and 100 % relative humidity, suppressed methanol permeability of 0.66 × 10−7 cm2 s−1, and the maximum power density of direct methanol fuel cell is 182.6 mW cm−2. Density functional theory was used to verify the important role of sulfamic acid in proton transfer, and the activation energy barriers under anhydrous and hydrous conditions are only 0.337 and 0.081 kcal, respectively. This study opens up new pathways for synthesizing NF composite PEMs. [ABSTRACT FROM AUTHOR]