Nafion-TiO₂ hybrid membranes for medium temperature polymer electrolyte fuel cells (PEFCs)

A nanocomposite re-cast Nafion hybrid membrane containing titanium oxide calcined at T = 400 °C as an inorganic filler was developed in order to work at medium temperature in polymer electrolyte fuel cells (PEFCs) maintaining a suitable membrane hydration under fuel cell operative critical conditions. Nanometre TiO₂ powder was synthesized via a sol-gel procedure by a rapid hydrolysis of Ti(OiPr)₄. The membrane was prepared by mixing a Nafion-dimethylacetammide (DMAc) dispersion with a 3 wt% of TiO₂ powder and casting the mixture by Doctor Blade technique. The resulting film was characterised in terms of water uptake and ion exchange capacity (IEC). The membrane was tested in a single cell from 80 to 130°C in humidified H₂/air. The obtained results were compared with the commercial Nafion115 and a home-made recast Nafion membrane. Power density values of 0.514 and 0.256 W cm^-2 at 0.56 V were obtained at 110 and 130°C, respectively, for the composite Nafion-Titania membrane. Preliminary tests carried out using steam reforming (SR) synthetic fuel at about 110°C have highlighted the benefit of the inorganic filler introduction when PEFC operates at medium temperature and with processed hydrogen.