Development of sulfonated poly (ether ether ketone) triaminopyrimidine nanocomposite membrane for direct methanol fuel cell

Abstract

Methanol crossover problem, which significantly occurred in direct methanol fuel cell (DMFC) using commercial Nafion® membrane, encouraged number of studies on the development of novel proton exchange membrane (PEM). This research was conducted to synthesize and characterize polymer-inorganic nanocomposite sulfonated poly (ether ether ketone) (SPEEK) membranes filled with Cloisite15A® clay by introducing 2,4,6-triaminopyrimidine (TAP) as a compatibilizer for direct methanol fuel cell (DMFC) application. The influences of different degree of sulfonation (DS) of SPEEK filled with Cloisite15A® and TAP loadings on the membrane properties were investigated. SPEEK with 63% of DS (SP63) was found to be the optimum membrane based on its higher overall membrane characteristics compared to SPEEK with other DS. Therefore, in this study, SP63 was chosen to be modified by adding various amounts of Cloisite15A®. The effect of clay loading on the physical properties of SPEEK nanocomposite membranes was studied. From the results, SPEEK mixed with 2.5 wt. % of Cloisite15A® (SP63/2.5CL) has been identified as the best composite formulation. Subsequently, various amounts of TAP were further incorporated into SP63/2.5CL formulation. The effect of TAP incorporation was characterized based on their thermal and physico-chemical properties such as thermal stability, ion exchange capacity (IEC), water uptake, methanol uptake, mechanical stability, proton conductivity and methanol permeability. A complete exfoliated nanocomposite structure of resultant nanocomposite membrane was confirmed by x-ray diffraction (XRD) and was supported by field emission scanning electron microscopy (FESEM). The resultant SPEEK/Cloisite15A®/TAP nanocomposite membranes characteristics were compared with the parent SPEEK and commercially Nafion®112 membranes. The highest power density of SPEEK nanocomposite membrane achieved was 39.4 mWcm-2, which is 46% higher compared to commercial Nafion®112 membrane. Due to its promising improved characteristics and performance, SP63/2.5CL/5.0TAP nanocomposite membrane could be chosen as the best polymer electrolyte membrane to be applied for DMFC application.