An overview of organic/inorganic membranes based on sulfonated poly ether ether ketone for application in proton exchange membrane fuel cells

Abstract

Nowadays, proton exchange membrane fuel cells (PEMFCs) are the most promising green energy <br />conversion devices for portable and stationary applications. Traditionally, these devices were based on<br />perfluoro-sulfonic acid electrolytes membranes, given the commercial name Nafion. Nafion is the most<br />used electrolyte membrane till now; because of its high electrochemical properties such as high proton<br />conductivity, good mechanical and chemical stability at fuel cell conditions, and .... However, its high <br />cost, reducing the performance at temperature higher than 80℃, and low humidity are the major<br />problems. Hydrocarbon polymers are encouraging alternative to Nafion, since they show the same or<br />even superior performance than Nafion at high temperature and low humidity by some modifications. <br />Numerous researches confirmed that Sulfonated poly ether ether ketone (SPEEK) is a promising PEM<br />because of its low-cost, low fuel cross over, and acceptable thermo-mechanical stabilities. However,<br />suitable proton conductivity in SPEEKs is depending on the high degree of sulfonation (DS), which<br />could deteriorate the mechanical properties of SPEEK membranes progressively at the high level. To<br />overcome this dilemma, various SPPEK-based hybrid/blend membranes are synthesized, and the<br />effects of the introduced fillers on their performance are investigated. The introduced inorganic<br />particles to the polymer membranes might be silica, zirconia, titania, heteropolyacids, carbon<br />nanotubes, and.... Enhanced proton conductivity, water retention at high temperatures, and higher<br />electrochemical properties are mentioned as some advantages of incorporating inorganic material into<br />the polymer matrix. High thermo-mechanical resistance and electrochemical activities are supplied by<br />inorganic moieties, while the organic parts supply plasticity and easier ductility at the low temperature.<br />Indeed, SPEEK blends have a good potential to alter Nafion at the high temperature and/or relatively<br />low humidity. In this paper, the last advances in progress of SPEEK-based organic/inorganic<br />composite membranes that perform truly under fuel cell conditions are discussed.