Browsing by Author "Uregen, Nurhan"

Now showing 1 - 2 of 2

Citation - WoS: 157
Citation - Scopus: 171
Development of Polybenzimidazole/Graphene Oxide Composite Membranes for High Temperature Pem Fuel Cells
(Pergamon-elsevier Science Ltd, 2017) Uregen, Nurhan; Pehlivanoglu, Kubra; Ozdemir, Yagmur; Devrim, Yilser
In this study, phosphoric acid doped Polybenzimidazole/Graphene Oxide (PBI/GO) nano composite membranes were prepared by dispersion of various amounts of GO in PBI polymer matrix followed by phosphoric acid doping for high temperature proton exchange membrane fuel cell (HT-PEMFC) application. The structure of the PBI/GO composite membranes was investigated by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and by thermogravimetric analysis (TGA). The introduction of GO into the FBI polymer matrix helps to improve the acid doping, proton conductivity and acid leaching properties. The SEM analyses have proved the uniform and homogeneous distribution of GO in composite membranes. The composite membranes were tested in a single HT-PEMFC with a 5 cm(2) active area at 165 degrees C without humidification. HT-PEMFC tests show that PBI/ GO composite membrane with 2 wt. % GO content performed better than bare PBI membrane at non humidified condition. At ambient pressure and 165 degrees C, the maximum power density of the PBI/GO-1 membrane can reach 0.38 W/cm(2), and the current density at 0.6 V is up to 0.252 A/cm(2), with H-2/air. The results indicate the PBI/GO composite membranes could be utilized as the proton exchange membranes for HT-PEMFC. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Citation - WoS: 145
Citation - Scopus: 163
Polybenzimidazole Based Nanocomposite Membranes With Enhanced Proton Conductivity for High Temperature Pem Fuel Cells
(Pergamon-elsevier Science Ltd, 2017) Ozdemir, Yagmur; Uregen, Nurhan; Devrim, Yilser
In this study, phosphoric acid doped PBI nanocomposite membranes were prepared by dispersion of various amounts of inorganic nanoparticles in PBI polymer followed by phosphoric acid (H3PO4) doping for high temperature proton exchange membrane fuel cells (HT-PEMFC). All of the PBI composite membranes were cast from the same FBI polymer with the same molecular weight. Titanium dioxide (TiO2), silicon dioxide (SiO2) and inorganic proton conductor zirconium phosphate (ZrP) were used as inorganic fillers. The PBI based composite membranes were characterized in terms of their acid uptake and acid leaching properties, mechanical properties, chemical stabilities in N-N Dimethylacetamide (DMAc) and impedance analyses. Thermal gravimetric analysis confirmed the improved thermal stability of the PBI composite membranes. The existence of inorganic fillers was improved the acid retention capability. Electrochemical Impedance Spectroscopy (EIS) showed that the introduction of 5 wt. % SiO2 or 5 wt. % ZrP helps to increase proton conductivity. The composite membrane with TiO2 retained low conductivity values than pristine PBI and this is a result of its non-uniform membrane structure. The highest proton conductivity of 0.200 S/cm was obtained for PBI/ZrP composite membrane with the highest value of H3PO4 doping level. Nyquist plots are drawn for all the membranes at different temperatures and the plots showed good fit with Randel's circuit. As a result the experimental results suggested that the PBI based composite membranes may be a promising electrolyte used in HT-PEMFC. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.