Synthesis and characterization of sulfonated poly (ether ether ketone)/graphene oxide nanocomposite for polymer electrolyte membrane

Abstract

The challenge of methanol crossover, which seriously occurred using commercial Nafion® membrane, urging the number of studies on the development of novel proton exchange membrane (PEM). The main objective of this research was to prepare and characterize sulfonated poly (ether ether) ketone (SPEEK)/graphene oxide (GO) nanocomposite as PEM. The influences of oxidation conditions particularly oxidant ratio, reaction temperature, and oxidation time on the GO properties were investigated. GO prepared with loading ratio 1:3, at reaction temperature 35°C and oxidation time 5 days was found to be the optimum GO which demonstrated excellent desired properties which abundantly available hydroxyl and epoxide groups. A fully exfoliated GO with high graphitic integrity was confirmed by x-ray diffraction (XRD) and was supported by x-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FESEM). Subsequently, this optimized GO with various loading amounts was chosen to be incorporated into the SPEEK solution and further studied. The effect of GO filler incorporation was investigated based on their physicochemical properties such as ion exchange capacity (IEC), swelling behavior, activation energy, proton conductivity, and methanol permeability. A fully exfoliated GO in SPEEK matrix was confirmed by XRD and was supported by FESEM and transmission electron microscopy (TEM). Besides, the resultant SPEEK/GO nanocomposite membranes characteristics were compared with the blank SPEEK and commercially Nation®115 membranes. SPEEK/GO nanocomposite with 2.5 wt.% GO loading possessed a strong interfacial interaction between SPEEK matrix and GO fillers, which offered a high proton conductivity (0.13 S.cm-1) with lower methanol permeability (3.69 x 10-7.cm2s-1) compared to commercial Nation®115 membranes. Hence, owing to its promising improved characteristics and performance, SPEEK/GO0.25 had been identified as the best composite formulation for PEM.