Sulfonated poly(ether ether ketone)/aminopropyltriethoxysilane/phosphotungstic acid hybrid membranes with non-covalent bond: Characterization, thermal stability, and proton conductivity

Sulfonated poly(ether ether ketone) (SPEEK) and aminopropyltriethoxysilane (KH550) hybrid membranes doped with different weight ratio of phosphotungstic acid (PWA) were prepared by the casting procedure, as well as PWA as a catalyst for sol-gel process of KH550. The chemical structures of hybrid membranes were characterized by energy dispersive X-ray spectrometry (EDX) and Fourier transform infrared spectroscopy (FTIR). The morphology of hybrid membranes was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results had proved the uniform and homogeneous distribution of KH550 and PWA in these hybrid membranes. The influence of the dispersed PWA on the properties of membranes such as thermal stability, water uptake, swelling ratio, and proton conductivity was researched. Thermogravimetry analysis (TGA) results indicated that the hybrid membranes had high thermal stability below 200 degrees C. The dimensional stabilities of the hybrid membranes were improved by addition of KH550-10/PWA compared with the pristine SPEEK The proton conductivity of the hybrid membrane with 5 wt.% PWA into SPEEK/KH550-10 reached the maximum of 0.084 S cm(-1) at 25 degrees C and 0.16 S cm(-1) at 80 degrees C under the 100% relative humidity condition. The proton conductivity mechanism in the hybrid membranes was discussed. Therefore, the possibility of the hybrid membranes for usage in proton exchange membrane fuel cells (PEMFCs) was explored. (C) 2008 Elsevier B.V. All rights reserved.