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Article Citation - WoS: 15Metal-Salt Enhanced Grafting of Vinylpyridine and Vinylimidazole Monomer Combinations in Radiation Grafted Membranes for High-Temperature PEM Fuel Cells(Amer Chemical Soc, 2020) Mojarrad, Naeimeh Rajabalizadeh; Sadeghi, Sahl; Kaplan, Begum Yarar; Guler, Enver; Gursel, Selmiye AlkanProton exchange membranes were prepared and characterized for utilization in high-temperature proton exchange membrane fuel cells, HT-PEMFCs. 1-vinylimidazole (1-VIm) and 4-vinylpyridine (4VP) monomers were simultaneously grafted onto pre-irradiated ETFE (ethylene-co-tetrafluoroethylene) films which were prepared using gamma-rays with a dose of 100 kGy, as a robust substrate to prepare acid-base composite membranes. The grafting reaction was performed at 60 degrees C for 24 h followed by protonation via phosphoric acid doping in the subsequent step. The effect of adding ferrous salts as promoters in grafting was investigated by characterization of resultant membranes via thermal gravimetric analysis and mechanical tests. The fuel cell tests were conducted under different relative humidities (RHs) and applied temperatures. Membranes prepared with salt addition exhibited superior proton conductivities. Results including up to 80 mS cm(-1) conductivity at 110 degrees C in 60% RH and excellent thermal stability, even at 300 degrees C, suggest these membranes are promising for HT-PEMFC applications.Article Citation - WoS: 24Citation - Scopus: 28Enhancing Proton Conductivity Via Sub-Micron Structures in Proton Conducting Membranes Originating From Sulfonated Pvdf Powder by Radiation-Induced Grafting(Elsevier Science Bv, 2018) Sadeghi, Sahl; Sanli, Lale Isikel; Guler, Enver; Gursel, Selmiye AlkanWe report here submicron-structured proton conducting poly(vinylidene fluoride)-graft-poly(styrene sulfonic acid) (PVDF-g-PSSA) membranes for polymer electrolyte membrane fuel cells (PEMFC). Highly conductive proton exchange membranes were obtained by single-step radiation grafting of sodium styrene sulfonate (SSS) to powder-form PVDF, followed by casting and subsequent solvent evaporation. The obtained submicron structure of membrane through solvent evaporation led to the arrangement of ionic channels proving increasing proton conductivity with the increase in graft level. In addition, a temperature above melting point of PVDF was used for solvent evaporation to allow melted PVDF to fill the formed pores, providing denser structure resulting in improved mechanical properties of the membranes. SSS grafting to PVDF powder was verified by NMR spectroscopy, and resultant membranes were characterized for proton conductivity, water up-take, morphology, mechanical and thermal properties, and fuel cell performance. According to preliminary tests, proton conductivities which were observed to increase with graft level were found to be around 70 mS cm(2) at 35% graft level. Thus, this led to a promising power density of 250 mW/cm(2) at 650 mA/cm(2).
