Post-mortem analysis of radiation grafted fuel cell membrane using X-ray photoelecton spectroscopy

Abstract

A post-mortem analysis of poly(tetrafluoroethylene-co-perfluorovinyl ether)-graft-polystyrene sulfonic acid (PFA-g-PSSA) membrane was carried out at the end of polymer electrolyte membrane (PEM) fuel cell test using X-ray photoelecton spectroscopy (XPS). The membrane was prepared by radiation-induced grafting of styrene onto PFA film using simultaneous irradiation technique followed by sulfonation reaction. The membrane was initially analyzed in its virgin state and the obtained data was used as a reference. The XPS results showed that the used membrane has undergone substantial structural changes, particularly in terms of chemical composition and concentration of its basic elemental components (Carbon, fluorine, oxygen and sulfur) as a result of degradation. This was found to be mainly due to the decomposition of polystyrene sulfonic side chain grafts. These results were confirmed by FTIR spectral analysis. It can be suggested that the oxidative degradation taking place in the PFA-g-PSSA membrane during fuel cell test is mostly due to the chemical attack at the tertiary hydrogen of -carbon of polystyrene side chain grafts. Moreover, XPS can be proposed as an effective tool for monitoring membrane degradation after fuel cell experiments.