Fabrication of nanocomposite membrane via combined electrospinning and casting technique for direct methanol fuel cell

Abstract

In the past decades, the emerging of nanotechnology has brought to the introduction of electrospinning process in polymer electrolyte nanocomposite membrane due to its specialty in providing a very large specific surface area which contributed by a small size of fillers and an outstanding nanovoids interconnectivity between the fillers. The objective of this study was to fabricate and characterize sulfonated poly (ether ether ketone) (SPEEK) nanocomposite membrane consist of electrospun Cloisite15A® (e-spun CL) for direct methanol fuel cell (DMFC) applications. Poly (ether ether ketone) polymer was sulfonated by sulfuric acid to obtain degree of sulfonation of 63%. SPEEK63/e-spun CL nanofibers were fabricated via electrospinning process in which SPEEK63 was used as carrier polymer while SPEEK63/e-spun CL nanocomposite membrane was obtained by casting method. Characterizations on physical, morphological and thermal properties of SPEEK63/e-spun CL were conducted and compared to SPEEK nanocomposite membrane with 2.5wt.% Cloisite15A® and 5.0wt.% triaminopyrimidine (SPEEK63/2.5CL/5.0TAP). Scanning electron microscopy (SEM) showed that Cloisite15A® was well electrospun with the nanofiber diameter ranging from 62.5 to 375 nm. Moreover, field emission scanning electron microscopy (FESEM) revealed that Cloisite15A® particles at nanometer range were uniformly distributed and 66% smaller than in SPEEK63/2.5CL/5.0TAP. In addition, x-ray diffraction proved that the dispersion state of Cloisite15A® fell into intercalated phase. A very small amount of Cloisite15A® (0.05wt.%) in SPEEK63/e-spun CL had successfully enhanced the proton conductivity up to 50% whereas, methanol permeability value was unfortunately 27 times higher than SPEEK63/2.5CL/5.0TAP. Proton conductivity and methanol permeability of SPEEK63/e-spun CL were 24.49 x 10-3 Scm-1 and 3.74 x 10-7 cms-1, respectively. Even though this study contributed to a selectivity of 95% lower than SPEEK63/2.5CL/5.0TAP, the electrospinning process had shown a promising technique to further reduce the original size of Cloisite15A® particles from mixed size (µm and nm) to nanometer size as well as by fine tuning the dispersion of Cloisite15A® can enhance SPEEK63/e-spun CL performance in DMFC applications.