Fluorine-Free Membranes Consisting of a Blend of S-PVA and PEBAX 1657 for Proton Exchange Membrane Fuel Cells: The Role of Titanium Dioxide Phosphate (TiO2PO4) Nanoparticle Fillers

Novel blend membranes containing S-PVA and PEBAX 1657 at a blend ratio of 8:2 were doped with varying amounts of titanium dioxide phosphate (TiO₂PO₄) as a nanoparticle filler at concentrations of 0, 3, 5, and 7 wt%. The membranes were fabricated using the solution-casting technique. The effect of the TiO₂PO₄ nanofiller on the polymer matrix was thoroughly investigated. Our aim was to investigate how the incorporation of TiO₂PO₄ nanofillers into non-fluorinated SPP-based membranes affects their structural, physicochemical, and electrochemical properties for application in fuel cells. Crystallinity of the samples was checked by means of X-ray diffraction (XRD), while FTIR was used to investigate the contact between the nanofiller and the polymers. The good compatibility resulted in strong interactions between the constituents and led to increased crystallinity of the membrane as well. Furthermore, SEM images confirmed the uniform distribution of the nanofiller. These structural features led to good thermal stability, as evidenced by thermogravimetric analysis (TGA), and good mechanical strength, as proved by tensile tests. Among the samples investigated, the highest water uptake of 51.70% was achieved on the composite membrane containing 3 wt% TiO₂PO₄, which also showed the highest ion exchange capacity at room temperature, reaching 1.13 meq/g. In line with these properties, among the synthesized membranes, the membrane labeled SPP 3% TiO₂PO₄ has the highest current density and power density, with values of 175.5 mA/cm² and 61.52 mW/cm², respectively.