SYNTHESIS OF HIGH TEMPERATURE RESISTANT MEMBRANE FORTHE FUEL CELLS


Thesis Type: Postgraduate

Institution Of The Thesis: Gazi Üniversitesi, Fen Bilimleri Enstitüsü, Turkey

Approval Date: 2007

Student: ALPAY ŞAHİN

Consultant: İRFAN AR

Abstract:

Proton Exchange membrane is regarded as the heart of PEM fuel cells. In order to fuel cell operates efficiently membrane must have some properties such as high proton conductivity and mechanical stability, ability to withstand the high temperatures, low cost, chemically inert and non toxic. The most widely used membranes are perfloro sulphonic acid membranes. But these membranes' proton conductivity is low at high temperatures and also they are very expensive. Because of these reasons alternative membranes are investigated. In this work, polystyrene and polyvinyl alcohol based organicinorganic composite membranes were synthesized by using different additives such as amberlyst, HZSM-5 Si/Al:50, HZSM-5 Si/Al:500, boric acid, boron phosphate and ludox. After membranes were synthesized, some characterization test such as; FT-IR, TGA-DSC, capacity of water uptake, capacity of ion exchange (IEC) and electrochemical impedance measurements (EIM) were performed. PVA+H3PO4 and PVA+H2SO4 based membranes show better properties. The highest proton conductivity values were obtained for the membranes coded as 0.1P-L40 (PVA + 0.1H3PO4 + 40% Ludox) and 0.01S-L40 (PVA + 0.01H2SO4 + 40% Ludox) under the experimental conditions of 60 ºC and 90 ºC respectively at 100% relative humidity. These values are 3.75 mS/cm and 4,77 mS/cm for the 0.1P-L40 and 0.01S-L40 respectively. As a result of thermo gravimetric analysis it was found that 0.1P-L40 coded membrane can stable up to 150ºC and 0.01S-L40 coded membrane can withstand the high temperatures up to 250ºC. Also these membranes' ion exchange capacities were measured as 6.26 meq/g and 5,02 meq/g respectively which are higher than the value reported for Nafion. The properties those are the results of the characterization tests show that synthesized membranes can be used in fuel cells.