ZrO 2–Nafion composite membranes for polymer electrolyte fuel cells (PEFCs) at intermediate temperature

Abstract

Recast Nafion composite membranes containing three different percentages (5%, 10% and 20%, w/w) of commercial Zirconium(IV) oxide as an inorganic filler were developed by the Doctor-Blade casting technique in order to work in direct hydrogen polymer electrolyte fuel cells (DH-PEFCs) in critical operative conditions for the fuel cell at a temperature of about 120–130 °C. By mixing a 10% (w/w) Nafion–dimethylacetammide (DMAc) dispersion with the inorganic compound, composite membranes were prepared. The developed membranes were characterised by water retention capacity (Wup%), ion exchange capacity (IEC, meq g −1), thermo-gravimetric analysis and by X-ray measurements. From XRD measurements, the ZrO 2 powder insertion was confirmed; the introduced amount was verified by TG analysis that highlighted the major thermal resistance of the developed membranes. Moreover, the chemical–physical results showed an increase of the water uptake and a decrease of the IEC with the increase of inorganic compound percentage. The introduction of the inorganic powder improved the mechanical characteristics of the developed composite membranes. Moreover, the membranes were tested in a 5 cm 2 commercial single cell from 80 °C to 130 °C in humidified H 2/air with pressures of 3.0 abs. bar and the obtained results compared to a bare Nafion recast membrane (N16) developed through the same method and used as a reference. Power density values of 604 mW cm −2 and of 387 mW cm −2 were obtained at 0.6 V and at T = 110 °C (100% of relative humidity) and T = 130 °C (85% RH), respectively, for the composite ZrO 2–Nafion membrane containing 10% (w/w) of inorganic filler.