Browsing by Author "Azhar, Masaud"

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    Mild sulfonated polyether ketone ether ketone ketone incorporated polysulfone proton exchange membrane
    (Universiti Teknologi Malaysia, 2022) Azhar, Masaud
    The main objective of this research is to develop composite membranes with appropriate water uptake, low swelling ratios, high thermal and oxidative stability with high proton conductivity. Ample evidence of post sulfonation and structure of the polyether ketone ether ketone ketone (PEKEKK) polymer under mild conditions was provided by proton nuclear magnetic resonance (1H NMR), Carbon-13 nuclear magnetic resonance (13C NMR) and fourier-transform infrared (FTIR) spectroscopic analysis respectively. Extended sulfonation time led to a greater degree of sulfonation (DS) and ion exchange capacity (IEC) values, indicating that more -SO3H groups were successfully incorporated into the polymer matrix. PSU/SPK-x and PSU/SPK/SGO-x proton exchange membranes (PEMs) were fabricated by incorporation of sulfonated polymer SPEKEKK (SPK) and sulfonated graphene oxide (SGO) as fillers in polysulfone (PSU) matrix to achieve high proton conductivity in fuel cells. The addition of SPK in PSU matrix showed significant improvement of proton conductivity. Scanning electron microscope (SEM) images of composite membranes confirmed the presence of SPK content in polymer matrix. According to morphological analysis, interfacial voids in membranes, in addition to sulfonic acid groups, enhanced proton conduction by establishing direct channels. The PSU/SPK-x composite membrane containing 30 wt.% SPK exhibited the highest proton conductivity of 0.12 S/cm at 90 oC. The results showed that the presence of SPK as proton conducting filler led to both high water uptake and proton conductivity than pristine PSU membrane. The increasing trend in proton conductivity with increasing SPK content thus validated the availability of water domains. However, membrane prepared with 15 wt.% loading ratio was found to be the suitable sample which demonstrated low mass losses and high thermal and oxidative stabilities as compared to 30 wt.%. Subsequently, SGO filler was incorporated into this optimized composite membrane for further studies. The addition of SGO filler in PSU/SPK/SGO-x membranes for 1.5 wt.% SGO showed the optimum conductivity of 0.03 S/cm at 90 oC. The ATR-FTIR spectra of all membranes showed all characteristic absorption bands and formation of separate layers. The field emission scanning electron microscope (FESEM) results confirmed the presence of sulfur content in PSU/SPK/SGO-x membranes. Water uptake in membranes reduced as the SGO filler concentration increased from 0.1 to 1.5 wt.%, however proton conductivity increased substantially due to higher bound water values, resulting in a significant improvement in conductivity from 60 to 90 oC. In short, the proton conductivities of both types of fabricated membranes in this work were significantly higher than those required for excellent PEM performance in fuel cell applications (10-2 S/cm). According to thermogravimetric analysis (TGA) of sulfonated polymer and composite membranes, the decomposition temperatures of sulfonic acid groups and main chain degradation of composite membranes were (tilde symbol)300 and (tilde symbol)500 oC respectively, suggesting excellent thermal stability properties. The PSU/SPK-15% and PSU/SPK/SGO-1.5% membranes were found to be intact, tough, and flexible even after 1 and 32 hours of treatment in Fenton's reagent at 80 oC, with retained weights of 99% to 98% and 90% to 72%, respectively, demonstrating excellent oxidative stability. These results imply the potential application of the fabricated composite membranes for fuel cell applications.