Synthesis of titania nanoparticle-dispersed hybrid membranes from allyloxytitanium and phosphonic acid derivatives for fuel cell

Inorganic-organic hybrid membranes consisting of an aliphatic backbone and amorphous TiO₂ nanoparticles (NPs) were synthesized from tetraallyloxytitanium and phosphonic acid methacrylate via a simple copolymerization-hydrolysis method. Tetraallyoxytitanium (TAT) was copolymerized with 2-hydroxyethyl methacrylate acid phosphate (HEMAP), and then hydrolyzed, yielding inorganic-organic hybrid composites. IR and ¹³C NMR spectroscopy confirmed the formation of the inorganic-organic hybrid structure. TEM and SAXS showed that amorphous TiO₂ NPs were dispersed in the polymer matrix. The membranes exhibited good thermal stability up to 180 °C. The aliphatic chains of the methacrylate derivative dispersed with TiO₂ NPs improved the mechanical properties of the membranes. The tensile modulus of the HEMAP/TAT membrane with a composition of 95:5 was 505 MPa. The conductivity of the 95:5 membranes was 4.1 × 10^-2 S cm^-1 at 130 °C and 100% relative humidity (RH), while it was 4.7 × 10^-4 S cm^-1 at 130 °C and 19.3% RH. The peak power of the 95:5 membrane was 4.8 mW/cm² at 140 °C and 30% RH. The cell utilizing the hybrid membrane was operated at 140 °C and 30% RH for 72 h without any drop in cell voltage.