Fabrication of SulfonatedPoly(ether ether Ketone)and Carbon Nano-Onions Composite Membranes for Enhanced Proton Exchangein Fuel Cells

Fuel cells play a vital role by offering a sustainable and eco-friendly energy solution, by tackling environmental issues and dependency on fossil fuels. However, still there is a problem of stability, sustainability, and cost of proton-exchange membrane (PEM). To address this concern, we synthesized a nanohybrid membrane of carbon nano-onions (CNOs) with sulfonated poly(ether ether ketone) (SPEEK) and polysulfone (PSF) by using a simple solution casting method. Synthesis of CNOs was done by a simple wick pyrolysis technique using waste frying oil. Fabricated nanohybrid membranes with varying concentration of CNOs were structurally, morphologically, thermally, mechanically, and chemically characterized by means of SEM, EDS, AFM, FTIR, XRD, TGA, 1H NMR, and CHNS. The FTIR spectra of all nanohybrid membranes indicate the existence of O═S═O vibrations at ∼1255 cm–1 (symmetric) and O═S═O at ∼1080 cm–1 (asymmetric) and intramolecular interactions between the components of nanohybrid membranes. 1H NMR and CHNS analyses confirm the presence of sulfonic groups in the polymeric matrices. The nanohybrid membranes are evaluated for water uptake (WU), local surface swelling ratio (SR), and oxidative stability. The optimized nanohybrid membrane shows 85.90 ± 2.43 of WU, 56.83 of local surface SR, and 94.28% of oxidative stability. Ion-exchange capacity and proton conductivity (at 70 °C) for the optimized nanohybrid membrane were determined as 1.43 ± 0.01 mmol g–1 and 0.613 mS cm–1, respectively. These results indicate the successful generation of proton transfer sites due to sulfonation on the polymer backbone and CNOs enhance all the parameters required for good PEM. Finally, observed findings demonstrate significant enhancements in SPEEK polymer properties by introducing CNOs, showcasing its potential as a PEM with various polymers, and introducing innovative possibilities for energy applications.