Browsing by Author "Sahin, Alpay"

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Improved Fuel Cell Properties of Nano-Tio2 Doped Poly(Vinylidene Fluoride) and Phosphonated Poly(Vinyl Alcohol) Composite Blend Membranes for Pem Fuel Cells
(Pergamon-elsevier Science Ltd, 2020) Yagizatli, Yavuz; Ulas, Berdan; Cali, Aygun; Sahin, Alpay; Ar, Irfan
Blend composite membranes are known as a good alternative to expensive Nafion membrane since they combine the superior properties of their components in a single structure. Herein, poly(vinylidene fluoride) (PVDF) phosphonated polyvinyl alcohol (PPVA) blend membranes (90/10 by mass) were prepared with the solution casting method. Then, nanoTiO(2) were added at varying mass ratios (2, 5, 8, 10, and 15%) to improve the performance of the synthesized membranes. Characterization tests namely, Fourier Transform Infrared (FTIR), water uptake capacity, ion exchange capacity (IEC), proton conductivity, dynamic mechanic analysis, open-circuit voltage (OCV) measurements, and performance tests were conducted. PVDF/PPVA membrane containing 8% nano-TiO2 exhibited the highest performance with 382.7 mA/cm(2) of current density and 225.4 mW cm(-2) of power density. The OCV measurements showed 8.57% voltage decrement at the end of 1000 h. Obtained results show the high potential of TiO2 doped PVDF/PPVA membranes could be considered as a favorable candidate for fuel cells. (c) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Investigation of Sulfonation Reaction Kinetics and Effect of Sulfonation Degree on Membrane Characteristics for Pemfc Performance
(Springer Heidelberg, 2022) Yagizatli, Yavuz; Ulas, Berdan; Sahin, Alpay; Ar, Irfan
There is a strong belief that sulfonated polyether ether ketone (SPEEK) can be used as an alternative to Nafion membrane in PEMFC applications due to its properties that can vary depending on sulfonation degree (DS). In this study, the temperature of the sulfonation reaction was kept constant at 50 degrees C, and SPEEK membranes were synthesized by altering the sulfonation time. The obtained membranes were characterized by proton nuclear magnetic resonance (H-NMR), Fourier transform infrared spectroscopy (FTIR), thermogravimetric and differential thermal analysis (TGA-DTA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), electrochemical impedance spectroscopy, water uptake capacity, swelling property, and ion exchange capacity tests (IEC). The kinetics of the sulfonation reaction was examined with experimental data and theoretically, the sulfonation degrees corresponding to the sulfonation time were determined. It has been ascertained that at least 4 h are required for the PEEK pellets to dissolve in sulfuric acid, while lower times are not sufficient for the sulfonation reaction. It has been determined that synthesized membranes have good thermal properties and the crystallization temperatures are independent of the sulfonation degree. Although the presence of sulfonic acid groups in the structure positively affected the water uptake capacity, ion exchange capacity, and hydration degree, deterioration was observed in the mechanical properties. High proton conductivity was obtained with the as-prepared membranes, and it was observed that activation energies were varied between 8.08 and 12.34 kJ/mol. The proton conduction law and transport mechanism have been determined to conform to the Arrhenius law and Grotthuss mechanism, respectively.
Preparation and Characterization of Speek-Pva Blend Membrane Additives With Colloidal Silica for Proton Exchange Membrane Fuel Cell
(Springer, 2024) Yagizatli, Yavuz; Ulas, Berdan; Sahin, Alpay; Ar, Irfan
An inexpensive membrane with high proton conductivity and high fuel cell performance, which can be an alternative to Nafion for PEMFC (Proton exchange membrane fuel cell), will overcome the obstacle to widespread commercialization of fuel cells due to high cost. For this purpose, SPEEK (sulfonated polyether ether ketone)-PVA (polyvinyl alcohol) blend membranes with colloidal silica additives were synthesized in this study. Ludox AS-40 was used as the colloidal silica source and the blend membrane was prepared by solution casting method. Water uptake capacity, swelling property, size change, dynamic mechanical analysis, ion exchange capacity, AC impedance analysis, hydrolytic and oxidative stability experiments of the synthesized Ludox additives blend membranes for fuel cell application were carried out, and the membranes were also characterized by FTIR (Fourier transform infrared) analysis. While the water uptake capacities of SPEEK/PVA membranes containing 1% Ludox, 5% Ludox, and 10% Ludox at room temperature were found to be 14.08%, 14.84%, and 16.6%, respectively, the water uptake capacities at 80oC increased to 14.73%, 15.17%, and 17.11%. The proton conductivities of 1% Ludox, 5% Ludox and 10% Ludox doped SPEEK/PVA membranes at 80oC were 0.25 S/cm, 0.56 S/cm, and 0.65 S/cm, respectively. Similarly, ion exchange capacities were determined to be 1.41 meq/g, 1.63 meq/g, and 1.71 meq/g, respectively. All Ludox-added membranes exhibited excellent hydrolytic stability, retaining approximately 88% of their mass after 650 h. In addition, in oxidative stability experiments carried out in 4 ppm Fe+ 2 at 80oC, the 10% Ludox-added membrane exhibited the highest weight loss of 88.8% at the end of 24 h, while the 5% Ludox-additive membrane retained 91.6% of its total weight. Considering the proton conductivity and longevity tests of the synthesized membranes, they are thought to be promising structures.