Proton conducting composite membranes from polyether ether ketone and heteropolyacids for fuel cell applications

Abstract

A series of composite membranes based on sulfonated polyether ether ketone with embedded powdered heteropolycompounds was prepared and their electrochemical and thermal properties were studied. An increase in degree of sulfonation as well as introduction of these fillers resulted in increased T g and enhanced membrane hydrophilicity, bringing about a substantial gain in proton conductivity. The conductivity of the composite membranes exceeded 10 −2 S/cm at room temperature and reached values of about 10 −1 S/cm above 100 • C.

Surface orientation of hydrophilic groups in sulfonated poly(ether ether ketone) membranes

“…The post sulfonation of PEEK (Victrex PLC) was run using concentrated sulfuric acid according to the procedure described elsewhere [9,18]. The process was detailed in supporting information.…”

“…The two main approaches to introduce sulfonic acid groups into this type of polymer are (a) the post-sulfonation of existing polymers, or (b) the direct copolymerization of sulfonated monomers [1]. The sulfonation reaction of commercial Victrex PEEK, yielding sulfonated poly(ether ether ketone), has been thoroughly investigated by various groups [6][7][8][9]. The post-sulfonation process is advantageous due to the availability of inexpensive commercial polymers, such as PEEK, and because of a relatively simple sulfonation procedure that can be scaled up.…”

“…The nomenclature of the aromatic protons for the SPEEK repeat unit was shown elsewhere [9,19]. The results are summarized in Table S2.…”

Proton conducting membranes based on cross-linked sulfonated poly(ether ether ketone) (SPEEK)

“…For water swellable or soluble samples with DS > 0.8, residual sulfuric acid was removed by dialysing the polymer. The polymer was then dried under vacuum for 1-2 days at 25-40 • C. The DS was determined by 1 H NMR according to the technique described elsewhere [5].…”

“…Many efforts have been recently undertaken to develop hydrocarbon based alternatives to Nafion, which would be less expensive and free from other disadvantages of perfluorinated membranes. Among the various polymers with diverse mechanical and electrical properties, long-term stability, efficiency and cost, which emerged over the last few years, membranes based on poly(ether ether ketone) (PEEK), were shown to be of considerable promise [1][2][3][4][5][6]. They were found to possess good thermal stability, appropriate mechanical strength and high proton conductivity, which depend on their degree of sulfonation (DS).…”