Transport properties and direct methanol fuel cell performance of sulfonated poly (ether ether ketone)/Cloisite/triaminopyrimidine nanocomposite polymer electrolyte membrane at moderate temperature

Abstract This paper presents an investigation on the transport properties represented by proton conductivity and methanol permeability of the sulfonated poly (ether ether ketone) (SPEEK) nanocomposite membranes filled with Cloisite 15A® clay (CC) compatibilized with 2,4,6-triaminopyrimidine (TAP) under various temperatures. The membranes were prepared through sulfonation of PEEK, followed by the formation of polymer composite dope by using solution intercalation and membrane casting. The composite membrane properties were evaluated using H NMR, field emission scanning electron microscope (FESEM), AC impedance spectroscopy and methanol diffusion test cell. The methanol permeability increased with the rise in temperature and reached a value of 0.52 × 10 −6  cm 2  s −1 at 60 °C; which coincided with proton conductivity of 47.10 mS cm −1 and a methanol selectivity of 9.1 × 10 4  S s cm −3 . The methanol permeability was found to be lower than that of Nafion® 117 membrane at all investigated temperatures. The nanocomposite SPEEK membranes were tested in a direct methanol fuel cell (DMFC), and the membrane denoted as SPEEK/CC2.5/TAP5.0 achieved a power density of 54.93 mW cm −2  at 60 °C. The results of this study suggest that SPEEK/CC2.5/TAP5.0 nanocomposite membrane has a potential to be an alternative polymer electrolyte for DMFC application.