Acid doped polybenzimidazole membranes for high temperature proton exchange membrane fuel cells

Download

index.pdf

Date

2007

Author

Yurdakul, Ahmet Özgür

Metadata

Show full item record

Item Usage Stats

189
views

183
downloads

Acid Doped Polybenzimidazole Membranes for High Temperature Proton Exchange Membrane Fuel Cells Author: Ahmet Özgür Yurdakul One of the most popular candidates for high temperature PEMFC’s is phosphoric acid doped polybenzimidazole (PBI) membrane due to its thermal and mechanical stability. In this study, high molecular weight PBI was synthesized by using PPA polymerization. The stirring rate of reaction solution was optimized to obtain high molecular weight. The inherent viscosity of polymer was measured at four points in 96 percent sulphuric acid solution at 30 degree centigrade by using an Ubbelohde viscometer. The highest average molecular weight was found as approximately 120,000 using the Mark-Houwink equation. The polymer was dissolved in N,N-dimethylacetamide at 70 degree centigrade with an ultrasonic stirrer. The membranes cast from this solution were doped with phosphoric acid solutions at different concentrations. The doping levels of the membranes were 6, 8, 10 and 11 moles phosphoric acid/PBI repeat unit. The mechanical strength of the acid doped membranes measured by tensile tests were found as 23, 16, 12 and 11 MPa, respectively. Conductivity measurements were made using the four probe technique. The membranes were placed in a conductivity cell and measurements were taken in humidity chamber with temperature and pressure control. The conductivity of membranes was measured at 110, 130 and 150 degree centigrade in both dry air and water vapor. The highest conductivity was 0.12 S/cm at 150 degree centigrade and 33 percent relative humidity for the membrane doped with 11 moles of H3PO4. The measurements showed that conductivity increased with increasing doping and humidity. Moreover, membranes had acceptable conductivity levels in dry air.

Subject Keywords

Chemical engineering.

URI

http://etd.lib.metu.edu.tr/upload/2/12608506/index.pdf
https://hdl.handle.net/11511/16926

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

High temperature proton exchange membrane fuel cells Ergün, Dilek; Eroğlu, İnci; Department of Chemical Engineering (2009) It is desirable to increase the operation temperature of proton exchange membrane fuel cells above 100oC due to fast electrode kinetics, high tolerance to fuel impurities and simple thermal and water management. In this study; the objective is to develop a high temperature proton exchange membrane fuel cell. Phosphoric acid doped polybenzimidazole membrane was chosen as the electrolyte material. Polybenzimidazole was synthesized with different molecular weights (18700-118500) by changing the synthesis condi...
Vulcan-Supported Pt Electrocatalysts for PEMFCs Prepared using Supercritical Carbon Dioxide Deposition Bayrakceken, Ayse; Smirnova, Alevtina; Kitkamthorn, Usanee; Aindow, Mark; Tuerker, Lemi; Eroğlu, İnci; ERKEY, CAN (Informa UK Limited, 2009-01-01) In this study, supercritical carbon dioxide (scCO(2)) deposition was used to prepare vulcan-supported Pt (Pt/Vulcan) electrocatalysts for proton exchange membrane fuel cells (PEMFCs), and the effects of process variables on the properties of the electrocatalysts were investigated. The two different methods used to reduce the organometallic precursor were thermal reduction in nitrogen at atmospheric pressure and thermal reduction in scCO(2). In the former method, the maximum Pt loading achieved was 9%, and t...
Acidity characterization and adsorption characteristics of cobalt and lead doped SBA15 mesoporous materials Güner, Özge; Üner, Deniz; Department of Chemical Engineering (2007) In this study, the surface acidity of Co and/or Pb doped SBA15 mesoporous catalysts were investigated by both diffuse reflectance fourier transform (DRIFT) infrared spectroscopy and transmission mode fourier transform infrared spectroscopy. Pyridine was used to identify the Brønsted and Lewis acid sites of the surface, at room temperature. From the DRIFT spectrum typical stretching vibrations of isolated terminal silanol (Si-OH) groups were observed for all the catalysts. These silanol group bands dissappea...
Quantum chemical simulation of nitric oxide reduction by ammonia (scr reaction) on v2o5 / tio2 catalyst surface Soyer, Sezen; Önal, Işıl; Department of Chemical Engineering (2005) The reaction mechanism for the selective catalytic reduction (SCR) of nitric oxide by ammonia on (010) V2O5 surface represented by a V2O9H8 cluster was simulated by density functional theory (DFT) calculations. The computations indicated that SCR reaction consisted of three main parts. In the first part ammonia activation on Brønsted acidic V-OH site as NH4+ species by a nonactivated process takes place. The second part includes the interaction of NO with pre-adsorbed NH4 + species to eventually form nitros...
DEPENDENCY OF NANOFLUID RHEOLOGY ON PARTICLE SIZE AND CONCENTRATION OF VARIOUS METAL OXIDE NANOPARTICLES YAPICI, Kerim; Osturk, Ozge; Uludağ, Yusuf (FapUNIFESP (SciELO), 2018-04-01) Impact of the nanoparticle size and concentration on the rheology of ethylene glycol based nanofluids containing nanoparticles of five different metal oxides is investigated. Particle mass concentrations ranged from 5 to 20 wt %. Types of the nanoparticles and their particle size are TiO2 (30 nm, 50 nm), MgO (20 nm, 40 nm), ZnO (10-30 nm, 35-45 nm, 80-200 nm), SiO2 (20-30 nm, 60-70 nm) and CuO (40 nm, 80 nm). A stress controlled rheometer fitted with a cone-and-plate system is employed for the rheological c...

Citation Formats

A. Ö. Yurdakul, “Acid doped polybenzimidazole membranes for high temperature proton exchange membrane fuel cells,” M.S. - Master of Science, Middle East Technical University, 2007.