Vibrational and Thermal Characterization of H₂O₂ Pretreatment Effects with Perfluorinated Sulfonic Acid Ionomer Membranes

Abstract

Perfluorosulfonated ionomer (PFSI) membranes have large applications in industrial electrochemical devices and, for that, several papers can be found in the literature dealing with their work performance and characterization. A vast majority of these follow some pretreatment steps with the membranes in which the main one involves H₂O₂ treatments at high temperatures, but there is very little study about this pretreatment effect and also if it changes or not the material properties. This work shows by IR and Raman spectroscopic techniques, TG, DSC and DMA measurements, that this treatment indeed changes slightly the PFSI polymer structures and also affects a little its thermal and mechanical properties. PAS-IR measurements show that H₂O₂ can promote oxidation reactions inside ionomer clusters while ATR-IR shows that, these reactions can cause a little change in its polymeric structure. TG, DMA and DSC analyses show that treated PFSI polymer is slightly more resistant to thermal effects but also becomes slightly more rigid and less plastic. The work also evaluates these effects in three perfluorinated ionomer samples with different equivalent weight (EW) values, showing that the lower the EW, the more pronounced are the treatment effects.