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

Abstract

Emergence of nanotechnology has resulted in the introduction of the electrospinning process in fabricating and characterising the polymer electrolyte membrane from the sulfonated poly (ether ether ketone) (SPEEK) nanocomposite membrane comprised of electrospun Cloisite15A® (e-spun CL) for direct methanol fuel cell (DMFC). Poly (ether ether ketone) polymer is sulfonated up to 63% by sulfuric acid. SPEEK63/e-spun CL nanofibers were fabricated via electrospinning in which SPEEK63 was used as carrier polymer while the SPEEK63/e-spun CL nanocomposite membrane was obtained by the casting method. Characterizations on physical, morphological and thermal properties of SPEEK63/e-spun CL were conducted and compared to the SPEEK membrane fabricated by casting simple mixing 2.5wt.% Cloisite15A® and 5.0wt.% triaminopyrimidine solution (SPEEK63/2.5CL/5.0TAP). Scanning electron microscopy (SEM) showed well electrospun Cloisite15A® with an average diameter nanofiber around 187.4 nm. Moreover, field emission scanning electron microscopy (FESEM) revealed that Cloisite15A® particles at a nanometer range were uniformly distributed and 66% smaller than those in SPEEK63/2.5CL/5.0TAP. Furthermore, x-ray diffraction proved that the dispersion state of Cloisite15A® fell into an intercalated phase. A very small amount of Cloisite15A® (0.05wt.%) in SPEEK63/e-spun CL successfully enhanced the proton conductivity up to 50%, whereas, unfortunately the methanol permeability value was 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 95% selectivity lower than SPEEK63/2.5CL/5.0TAP, electrospinning showed a promising technique to further reduce original sized Cloisite15A® particles from mixed size (μm and nm) to nanometer sized. In addition, by fine tuning, the dispersion of Cloisite15A® enhances the SPEEK63/e-spun CL performance in DMFC.