Composite membranes comprising sulfonated poly (ether ether ketone) (SPEEK) blended with varying proportions of sulfo ethyl cellulose (SEC) at 5 wt% and 10 wt% were fabricated for fuel cell application. The structural, morphological, and thermal properties of these membranes were investigated using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis. The composite membranes exhibited enhanced thermal stability and increased water absorption compared to the pristine SPEEK. Moreover, the proton conductivity of the composite membranes surpassed that of pure SPEEK, reaching up to 110 mS/cm at temperatures exceeding 100 °C…Read more