Membrane modification by liquid phase deposition using small amount of TiO2 for high-temperature operation of polymer electrolyte fuel cells

A TiO2-dispersed Nafion (Nafion–TiO2) membrane is prepared by the liquid phase deposition (LPD) method by carrying out a hydrolysis reaction of titanium–fluoro complex in an aqueous solution. The conductivity of the TiO2-modified membrane is studied. The obtained composite membrane has dispersed TiO2 nanoparticles which enhance the membrane's hydrophilic and hygroscopic properties of polymer electrolyte fuel cells (PEFCs) under high temperature conditions. Change in the amount of TiO2 deposited on the Nafion membrane from 0.07 to 0.18 wt% for LPD reaction periods ranging from 3 to 9 h does not result in any change in the membrane's ion-exchange capacities. High resolution transmission electron microscopy (HRTEM) images indicate the growth and agglomeration of TiO2 particles at the surface during the LPD reaction. The diffusion of TiO2 is observed in the membrane from its surface up to a depth of ca. 20 μm by means of XPS measurement. The water retention capacity of the membrane is improved from 63% to 83% at 200 °C by the deposition of 0.18 wt% of TiO2. Consequently, we find the small amount of TiO2 improved water management and increase the proton conductivity.

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► We prepared TiO2-dispersed Nafion membrane by the liquid phase deposition method.
► Such membrane can improve the water management by existing hydrophilic filler.
► The amount of loading TiO2 is much lower than previous reports.
► Water management was much improved after deposition despite the amount was so low.
► This material can contribute to PEFCs operating at high temperature.