Physicochemical characterization of low sulfonated polyether ether ketone/Smectite clay composite for proton exchange membrane fuel cells

Polyether ether ketone (PEEK) with a low sulfonation degree was blended using different proportions of sodium rich Smectite clay (3 and 6 wt%) to use as an electrolyte membrane for fuel cell application. The structural functionalities, surface morphologies, and the thermal stability of the resultant composite membranes were characterized using Fourier-transform infrared spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, atom force microscopy, and thermo-gravimetric analysis. FT-IR showed that no chemical reactions take place between the sulfonated polyether ether ketone (SPEEK) and the clay with different ratios. XRD diffractograms illustrated a lower degree of crystallinity of the blended SPEEK than pristine SPEEK. The elaborated composite membranes proved to have a higher thermal stability than SPEEK. Furthermore, the SPEEK/clay composite membranes with 3 and 6 wt% in clay loading had higher water uptake and lower methanol uptake than those in pristine SPEEK It was also shown that, the incorporation of sodium ions rich Smectite clay layers between the clusters in SPEEK improved the conductivity to 2 x 10(-2)S/cm at 140 degrees C (for 6 wt% in clay) without compromising the dimensional stability of the composite membranes. These results propose the composite membranes as a potential candidate for methanol fuel cells at temperatures above 120 degrees C making SPEEK composite membrane competitive to that of Nafion membrane.

Automated summary

The study blended low sulfonation degree polyether ether ketone (PEEK) with different proportions of sodium-rich Smectite clay to use as an electrolyte membrane for fuel cell application. The composite membranes showed higher thermal stability, lower crystallinity, and increased conductivity, making them potential candidates for methanol fuel cells at temperatures above 120 degrees C, competitive to Nafion membrane.