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Article Citation - WoS: 61Citation - Scopus: 73Evaluation of Sulfonated Polysulfone/Zirconium Hydrogen Phosphate Composite Membranes for Direct Methanol Fuel Cells(Pergamon-elsevier Science Ltd, 2017) Ozden, Adnan; Ercelik, Mustafa; Devrim, Yilser; Colpan, C. Ozgur; Hamdullahpur, FeridunDirect methanol fuel cell (DMFC) technology has advanced perceivably, but technical challenges remain that must be overcome for further performance improvements. Thus, in this study, sulfonated polysulfone/zirconium hydrogen phosphate (SPSf/ZrP) composite membranes with various sulfonation degrees (20%, 35%, and 42%) and a constant concentration of ZrP (2.5%) were prepared to mitigate the technical challenges associated with the use of conventional Nafion (R) membranes in DMFCs. The composite membranes were investigated through Scanning Electron Microscopy (SEM), Electrochemical Impedance Spectroscopy (EIS), Thermogravimetric Analysis (TGA), oxidative stability and water uptake measurements, and single cell testing. Comparison was also made with Nafion (R) 115. Single cell tests were performed under various methanol concentrations and cell temperatures. Stability characteristics of the DMFCs under charging and discharging conditions were investigated via 1200 min short-term stability tests. The response characteristics of the DMFCs under dynamic conditions were determined at the start-up and shut-down stages. Composite membranes with sulfonation degrees of 35% and 42% were found to be highly promising due to their advanced characteristics with respect to proton conductivity, water uptake, thermal resistance, oxidative stability, and methanol suppression. For the whole range of parameters studied, the maximum power density obtained for SPSf/ZrP-42 (119 mW cm (2)) was found to be 13% higher than that obtained for Nafion (R) 115 (105 mW cm (2)). (C) 2017 Elsevier Ltd. All rights reserved.Article Citation - WoS: 75Citation - Scopus: 89Investigation of Nafion Based Composite Membranes on the Performance of Dmfcs(Pergamon-elsevier Science Ltd, 2017) Ercelik, Mustafa; Ozden, Adnan; Devrim, Yilser; Colpan, C. OzgurIn this study, Direct Methanol Fuel Cells (DMFCs) based on composite membranes (Nafion/ SiO2 and Nafion/TiO2) were manufactured; and their performances were compared with that of the DMFC based on Nafion (R) 115 membrane. For this purpose, composite membranes were synthesized applying the recasting method with the inorganic particle loading of 2.5 wt%. The structures of these composite membranes were investigated by Scanning Electron Microscopy (SEM), proton conductivity measurement and water uptake measurement. Ultrasonic coating technique was used in the manufacturing of the Membrane Electrode Assemblies (MEAs). The performance tests of the composite membranes were conducted using in-house experiments. In these tests, the effect of methanol concentration (0.75, 1, and 1.5 M) on the performance of the MEA having Nafion 115 was investigated at 80 degrees C to find the value of the methanol concentration that yields the highest power density. This study showed that the MEA operating at 1 M gives the highest performance. Then, the performance of this MEA was compared with that of the MEAs having Nafion/ SiO2 and Nafion/TiO2 composite membranes in single cell DMFC setup at 60 degrees C, 80 degrees C, and 95 degrees C. The results of these experiments demonstrated that the MEA having Nafion/TiO2 composite membrane provides much better performance with the maximum power density values of 422.04 W/m(2), 641.16 W/m(2), and 710.88 W/m(2) at 60 degrees C, 80 degrees C, and 95 degrees C, respectively. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
