In this study, sulfonated graphene oxide (SGO)/Fe₃O₄ nanosheets were synthesized by hydrothermal method and incorporated into blend sulfonated poly(ether ether ketone) (SPEEK)/poly(vinyl alcohol) (PVA) matrix with different weight percent of (SGO)/Fe₃O₄ nanosheets. The performances of prepared membranes were investigated by water uptake, membrane swelling, mechanical and thermal stability, proton conductivity, methanol permeability and DMFC test. It was found that the water uptake and tensile strength of SPEEK membrane increased and proton conductivity and power density decreased by blending with PVA. Incorporation of SGO/Fe₃O₄ nanosheets into SPEEK/PVA matrix enhanced mechanical stability, proton conductivity and methanol barrier properties of membrane. The SPEEK/PVA/SGO/Fe₃O₄ nanocomposite membrane with optimal nanosheets content (5 wt%) exhibits low methanol permeability (8.83 × 10⁻⁷ cm² s⁻¹), high tensile strength (51.2 MPa), high proton conductivity (0.084 S cm⁻¹ at 25 °C) and high power density (122.7 mW cm⁻² at 80 °C) and suggests its potential application in DMFCs.

In this work, the application of a sulfonated poly(ether ether ketone) (SPEEK)/amine functionalized titanium dioxide nanoparticle (AFT) composite as a novel membrane in proton exchange membrane fuel cells (PEMFC) was studied. Titanium dioxide (TiO₂) nanoparticles were functionalized by grafting aminopropyl groups through hydrolysis of 3-aminopropyltriethoxysilane (APTES). The influence of the AFT nanoparticles on thermal and mechanical stability, water uptake, dimensional stability and electrochemical properties of the membranes were studied. The grafting of APTES onto TiO₂ nanoparticles improved their dispersion in the SPEEK matrix. The nanocomposite membrane with the optimal amount of AFT nanoparticles, 7.5 wt%, showed a proton conductivity of 0.135 S cm⁻¹ at 80 °C which was 159.6% higher than that of the nanocomposite membrane with 7.5% TiO₂. This can be attributed to their good dispersion and reduction of interparticle separation spacing which creates connected pathways for proton transport. The membrane with 7.5 wt% AFT showed a 40.8% decrease in swelling, a 132.7% increase in conductivity and an 86.7% increment in maximum power density (PD_max) (230 mW cm⁻²) compared with the pristine SPEEK membrane, which indicated its potential application in PEMFCs.