چكيده به لاتين
Simultaneous high proton conductivity with high oxidative stability is one of the major concerns in the proton exchange membrane (PEM) preparation. With this perspective, series of hybrid membranes were prepared by doping an optimized amount of three sulfated metal oxides: titania, zirconia, and zirconia-titania, into the sulfonated poly ether ether ketone (SPEEK) matrix. The nanoparticles were synthesized using sol-gel method and specified by XRD, TEM, and EDS analysis. Two models for correlation of proton conductivity and oxidative stability (in Fenton solution) with two independent factors, including sulfonation time and the weight percent of the nanoparticle loading, were obtained by central composite design for each nanoparticle. The nanoparticle loading was found to be the more significant factor in the proton conductivity model, while the sulfonation time in the oxidative stability model was the main affecting factor. The optimal membranes were characterized through structural, morphological, thermochemical and mechanical tests. The results indicate that the introduction of the optimal contents of sulfated nanoparticle into the polymer matrix would improve the water uptake and consequently the proton conductivity at a higher temperature while keeping the swelling ratio at an acceptable range. The highest achieved proton conductivity by the resulted nanocomposite (SPEEK/STi) was 37.35 mS cm-1 at 120 ℃ with more than 300-minute durability in the Fenton's reagent. The single-cell performance test of nanocomposite based MEA at 90℃ and 100% RH exhibited a peak power density of 281 mW cm-2 at 601 mA cm-2, which was 1.5 times more than commercial MEA at the same condition. Acceptable dispersion of nanoparticle in the SPEEKmatrix causes negligible fuel crossover flux (e.g. 0.35×10-6 mmol s-1 cm-2 and12.49 × 10-6 mmol s-1 cm-2 for nanocomposite-based MEA and commercial MEA, respectively), which is indispensable to improve the mechanical and chemical stability. Accordingly, sulfated metal oxide nanocomposite SPEEK-based membranes are promising alternative polymer electrolyte membrane for fuel cell applications.
