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

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