Stable and hydroxide ion conductive membranes for fuel cell applications: Chloromethyaltion and amination of poly(ether ether ketone)

Poly(ether ether ketone) (PEEK) was dissolved in conc. H2SO4 and its chloromethylation was achieved in presence of paraformaldehyde, trimethylchlorosilane and Lewis acid catalyst, obtained about 35–75% degree of chloromethylation (DCM). This idea is based on partial sulfonation of PEEK to make it soluble and further complete replacement of –SO3H with –CH2Cl groups. Alkaline membranes (AMs) were prepared by quaternization of chloromethylated PEEK (CMPEEK). The reported method is a “green” alternative for the production of AEM without the use of hazardous chemicals (such as chloromethyl methyl ether, chloromethyloctylether, bis(chloromethyl) ether etc.). Chronopotentiometry study of prepared membranes confirmed their homogeneous and alkaline nature suitable for methanol fuel cells. The AMs exhibit a splendid chemical stability at 10 M KOH. Alkaline conductivity of quaternized poly(ether ether ketone) membrane with 75% DCM (QPEEK-75) (14.63 mS cm−1) in equilibration with deionized water was relatively high in compare with other AMs reported in the literature. For the H2/air single fuel cell at 50 °C with QPEEK-75 membrane, about 1.02 V OCV and 48.09 mW cm−2 power density at 109.3 mA cm−2 current density were obtained.