Study of hydrogen crossover and proton conductivity of self-humidifying nanocomposite proton exchange membrane based on sulfonated poly (ether ether ketone)

Abstract

Fuel crossover and proton conductivity in proton exchange membranes have considerable effects on the performance of polymer electrolyte membrane fuel cells. In the present study, a self-humidifying nanocomposite membrane based on SPEEK (Sulfonated poly ether ether ketone) and Cs2.5H0.5PW12O40 supported Pt catalyst was prepared and its hydrogen crossover and proton conductivity were investigated. Hydrogen crossover was evaluated by LSV (linear sweep voltammetry) as a function of temperature, RH (relative humidity) and hydrogen partial pressure. Design of experiments by RSM (response surface methodology) was used for investigating the effects of the related parameters. Increasing each of the parameters leads to increase the gas crossover. In addition, the proton conductivity was measured by EIS (electrochemical impedance spectroscopy) as a function of temperature and relative humidity and a mathematical relationship was obtained based on the experimental data. Note that all of the mentioned tests were performed on Nafion117 membranes in order to compare the obtained results. Then, performance of the both membranes was compared based on TPI (transport performance index) at the end. The results show that in the same operating conditions, the value of TPI in the SPEEK nanocomposite membrane was less than that of Nafion117. Therefore, the self-humidifying SPEEK membrane shows a better performance in transport properties.