title: Synthesis and Properties of Poly(ether sulfone)s with Clustered Sulfonic Groups for PEMFC Applications under Various Relative Humidity.
abstract: Novel sulfonated poly(ether sulfone) copolymers (S4PH-x-PSs) based on a new aromatic diol containing four phenyl substituents at the 2, 2', 6, and 6' positions of 4,4'-diphenyl ether were synthesized. Sulfonation was found to occur exclusively on the 4 position of phenyl substituents by NMR spectroscopy. The ion exchange capacity (IEC) values can be controlled by adjusting the mole percent (x in S4PH-x-PS) of the new diol. The fully hydrated sulfonated poly(ether sulfone) copolymers had good proton conductivity in the range 0.004-0.110 S/cm at room temperature. The surface morphology of S4PH-x-PSs and Nafion 212 was investigated by atomic force microscopy (tapping-mode) and related to the percolation limit and proton conductivity. Single H2/O2fuel cell based on S4PH-40-PS loaded with 0.25 mg/cm2catalyst (Pt/C) exhibited a peak power density of 462.6 mW/cm2, which was close to that of Nafion 212 (533.5 mW/cm2) at 80 °C with 80% RH. Furthermore, fuel cell performance of S4PH-35-PS with various relative humidity was investigated. It was confirmed from polarization curves that the fuel cell performance of S4PH-35-PS was not as high as that of Nafion 212 under fully hydrated state due to higher interfacial resistance between S4PH-35-PS and electrodes. While under low relative humidity (53% RH) at 80 °C, fuel cells based on S4PH-35-PS showed higher peak power density (234.9 mW/cm2) than that (214.0 mW/cm2) of Nafion 212.
authors.affiliation: Department of Materials Science and Engineering, National Taiwan University of Science and Technology , Taipei 10617, Taiwan.
authors.forename: Shih-Wei
authors.initials: SW
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering, National Taiwan University of Science and Technology , Taipei 10617, Taiwan.
authors.forename: Jyh-Chien
authors.identifier: http://orcid.org/0000-0002-8630-4966
authors.initials: JC
authors.lastname: Chen
authors.affiliation: Material and Chemical Research Laboratories Division of Polymer Research, Industrial Technology Research Institute , Hsinchu 30011, Taiwan.
authors.forename: Jin-An
authors.initials: JA
authors.lastname: Wu
authors.affiliation: Institute of Atomic and Molecular Science, Academia Sinica , Taipei 10617, Taiwan.|Center for Condensed Matter Sciences, National Taiwan University , Taipei 10617, Taiwan.
authors.forename: Kuei-Hsien
authors.initials: KH
authors.lastname: Chen
keywords: fuel cell; power density; proton exchange membrane; relative humidity; sulfonated poly(ether sulfone)