Selective Proton-Conducting Polystyrene-Based Polyelectrolyte Membrane Containing Bi₂O₃ Nanoparticles and Graphitic Carbon Nitride Nanosheets for Fuel Cells and Supercapacitors

The focus of this research is to design and develop polystyrene- block -poly(ethylene- ran -butylene)- block -polystyrene (PSEBS) membranes doped with bismuth oxide pyrolyzed with graphitic carbon nitride (Bi 2 O 3 -GCN). The substantial concentration of Bi 2 O 3 -GCN in the acidic moieties of the hydrophilic polymer promotes phase separation, resulting in good phase morphology. The bond stretching, crystallinity, and thermal stability of the sulfonated PSEBS and composite membranes were characterized using FT-IR, XRD, and TGA. The S-PSEBS/Bi 2 O 3 -GCN membrane was fabricated as a flexible solid-state electrolyte in symmetric supercapacitors and as an electrolyte in proton exchange membrane fuel cells (PEMFCs). For use in PEMFC, physicochemical and electrochemical characterizations were performed, and it was found that during the addition of Bi 2 O 3 -GCN, the conductivity reached a value of 0.0547 S/cm for S-PSEBS/Bi 2 O 3 -GCN-8, whereas S-PSEBS exhibits 0.018 S/cm. The composite membrane loaded with 8.0 wt % Bi 2 O 3 /GCN produced a maximum peak power density of 19 mW/cm 2 . Activated carbon as a positive and negative electrode and Bi 2 O 3 -GCN membrane were assembled in a symmetric supercapacitor. The symmetric supercapacitor achieved a maximum voltage of up to 1.2 V and power and energy density up to the maximum values of 182.7 W kg –1 and 46.2 W h kg –1 . The combination of the S-PSEBS/Bi 2 O 3 -GCN polymer membrane enables the pathway to enhance the effective material for energy conversion of fuel cell and energy storage of symmetric supercapacitor.