Title of Paper:Quaternary phosphonium-functionalized poly(ether ether ketone) as highly conductive and alkali-stable hydroxide exchange membrane for fuel cells

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Date of Publication:2014-09-15

Journal:JOURNAL OF MEMBRANE SCIENCE

Included Journals:SCIE、EI、Scopus

Volume:466

Page Number:220-228

ISSN No.:0376-7388

Key Words:Poly(ether ether ketone); Quaternary phosphonium; Phosphonization; Hydroxide exchange membrane; Alkaline membrane fuel cells

Abstract:A series of quaternary phosphonium-functionalized poly(ether ether ketone)s (PEEK-QPOHs) have been synthesized by phosphorization reaction, and their membranes have been prepared by a solution casting method. Ion exchange capacity (IEC) of PEEK-QPOH membranes ranges from 0.89 to 1.19 mmol g(-1) with the degree of chloromethylation from 70% to 126%. Not only are PEEK-QPOH polymers soluble in typical high-boiling-point membrane-forming solvents, but also they are soluble in some low-boiling-point water-miscible solvents (low alcohols), implying their ability to serve as both membranes and ionomers. PEEK-QPOH membranes showed high hydroxide conductivity, e.g., a PEEK-QPOH 126% membrane (with IEC of 1.19 mmol g(-1)) exhibited 61 and 89 mS cm(-1) at 20 degrees C and 60 degrees C, respectively. Based on the same polymer backbone of PEEK, quaternary phosphonium-functionalized PEEK membranes are more hydroxide-conductive and more alkali-stable than quaternary ammonium- and imidazolium-functionalized counterparts. All these properties indicate PEEK-QPOH is one of the most promising HEM materials for potential applications in alkaline membrane fuel cells. (C) 2014 Published by Elsevier B.V.