Preparation and Characterization of a Novel Sulfonated Titanium Oxide Incorporated Chitosan Nanocomposite Membranes for Fuel Cell Application

In this study, nano-TiO(2) sulfonated with 1,3-propane sultone (STiO(2)) was incorporated into the chitosan (CS) matrix for the preparation of CS/STiO(2) nanocomposite membranes for fuel cell applications. The grafting of sulfonic acid (–SO(3)H) groups was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis and energy-dispersive X-ray spectroscopy. The physicochemical properties of these prepared membranes, such as water uptake, swelling ratio, thermal and mechanical stability, ion exchange capacity and proton conductivity, were determined. The proton conducting groups on the surface of nano-TiO(2) can form continuous proton conducting pathways along the CS/STiO(2) interface and thus improve the proton conductivity of CS/STiO(2) nanocomposite membranes. The CS/STiO(2) nanocomposite membrane with 5 wt% of sulfonated TiO(2) showed a proton conductivity (0.035 S·cm(−1)) equal to that of commercial Nafion 117 membrane (0.033 S·cm(−1)). The thermal and mechanical stability of the nanocomposite membranes were improved because the interfacial interaction between the -SO(3)H group of TiO(2) and the –NH(2) group of CS can restrict the mobility of CS chains to enhance the thermal and mechanical stability of the nanocomposite membranes. These CS/STiO(2) nanocomposite membranes have promising applications in proton exchange membrane fuel cells.