Proton-conducting phosphotungstic acid/sulfonated fluorinated block copolymer composite membrane for polymer electrolyte fuel cells with reduced hydrogen permeability

Ae Rhan Kim, Vinothkannan Mohanraj, Jong Seok Kim, Dong Jin Yoo

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)

Abstract

A sulfonated fluorinated block copolymer (SFBC) consisting of sulfone and ether bridges was synthesized via nucleophilic substitution polymerization, and then incorporated with 10, 20 or 30 wt% of phosphotungstic acid (PWA) using facile solution casting approach to fabricate composite membranes. The monomer sulfonation was carried out for SFBC to avoid the random sulfonation that can degrade the mechanical strength of polymer chains. A higher local concentration of acidic moieties within molecular frameworks of PWA and good mechanical properties allow for an unprecedented approach to tailor the proton conductivity as well as mechanical strength of composite membrane, as evidenced by alternating current (AC) impedance and dynamic mechanical (DMA) analyses. The surface morphological properties and roughness of membranes were investigated by field emission scanning electron microscope (FE-SEM) and atomic force microscope (AFM); the composite membranes exhibited even and denser dispersion of PWA in polymer matrix. Compared to pristine SFBC-50, the water uptake, hydrophilicity and ion exchange capacity of SFBC-50/PWA-X membranes were significantly improved. The peak proton conductivity of SFBC-50/PWA-30 membrane at 90 °C under 100% relative humidity (RH) is 105.22 mS/cm, which is 2.55 folds higher than that of pristine SFBC-50 (41.11 mS/cm) and 1.2 folds lower than that of Nafion-117 membrane (127.12 mS/cm). The peak power density delivered by the PEFC containing SFBC-50/PWA-30 membrane is 377.83 mW/cm2 at a load current of 864.29 mA/cm2 while operating the cell at 60 °C under 100% RH. In contrast, under identical condition, the pristine SFBC-50 membrane delivered the peak power density of 147.37 mW/cm2 at a load current of 353.52 mA/cm2, a 2.56-fold lower performance compared to composite membrane. Furthermore, composite membrane exhibited much lower H2 permeability compared to that of SFBC-50 and Nafion-117 membrane
Original languageEnglish
Pages (from-to)2779–2804
Number of pages26
JournalPolymer Bulletin
Volume75
Early online date14 Sept 2017
DOIs
Publication statusPublished - 1 Jul 2018
Externally publishedYes

Funder

This work (Grants No. S2136752) was supported by Business for Cooperative R&D between Industry, Academy, and Research Institute funded Korea Small and Medium Business Administration in 2013.

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