An investigation of proton conductivity of nanocomposite membranes based on sulfated nano-titania and polymer

The synthesis and physicochemical properties of the nanocomposite polymer electrolyte membranes were investigated throughout this work. The materials were prepared via two different approaches where in the first, a binary system was produced by mixing of poly(1-vinyl 1,2,4-triazole) (P(VTri))/sulfated nanotitania (TS) and poly(vinylphosphonic acid) (P(VPA))/sulfated nanotitania (TS) composites. In the second, ternary nano-composite membranes including P(VTri)/TS/P(VPA) were produced at several compositions to get P(VTri)–TS–P(VPA)x where x designates the molar ratio of the polymer repeating units and sulfated nanotitania ratio. The complex structure of the polymers as well as the interaction of functional nano-particles with the matrix were investigated by FT-IR spectroscopy. TGA results verified that the presence of sulfated nanotitania and P(VTri) in the complex polymer electrolytes suppressed the formation of phosphonic acid anhydrides and thermal stability increased up to approximately 300 °C. The DSC results indicate that the Tg of the materials shifts to lower temperatures as P(VPA) content increases. SEM results showed the homogeneity of the nanocomposite membrane systems. Proton conductivity of the membranes was also measured at the anhydrous state. The conductivity of P(VTri)–TSP(VPA)4 is found to be 0.003 (S cm− 1) at 150 °C. The sulfated nanotitania particles in the composite membranes improved the thermal and mechanical properties and enhanced the proton conductivity.