Nanocomposite membranes prepared from sulfonated polyether ether ketone (SPEEK) and nanocaly for enhancement of fuel cell properties

Abstract

Sulfonated polyether ether ketone (SPEEK) polymer nanocomposite membranes were fabricated by incorporating nanoclays (e.g., cloisite 30B) and bentonite into the SPEEK polymer matrix. The SPEEK, SPEEK/cloisite, SPEEK/bentonite and SPEEK/cloisite/bentonite nanocomposite membranes were prepared by using solution intercalation method where the thickness of the membranes was approximately 100 μm. The membranes were characterized by FTIR, SEM, H1 NMR and TGA/DSC to investigate the influence of thermal and physical properties of SPEEK polymer membranes with the adding of nanoclays into SPEEK polymer matrix. The sulfonation of PEEK was confirmed by Fourier transform infrared spectroscopy (FTIR) and the degree of sulfonation of PEEK was determined by H1 NMR spectroscopy. The modified membrane (SPEEK/cloisite/bentonite) showed 2.1% reduced percent water uptake compared to the pristine SPEEK membrane and it showed enhanced thermal strength. Improved glass transition temperature of 7 °C was observed for the modified membrane. The presence of nanoclays into the modified SPEEK polymer membranes was confirmed by scanning electron microscopy (SEM) and TGA/DSC. The performance of the membranes was determined by their water uptake capacity, methanol permeability and proton conductivity. The maximum proton conductivity showed by the SPEEK/cloisite membrane at 80 °C and fully hydrated condition was 3.0549 × 10-3 S cm-1. The SPEEK/cloisite/bentonite nanocomposite membranes showed reduced proton conductivity; however, they also predicted a 6.14% reduction in methanol permeability as compared to pristine SPEEK membrane, hereby, suggesting that the modified membrane is acceptable for direct methanol fuel cell.