Composite Nafion Membranes Containing Nanosize TiO2/SnO2 for Proton Exchange Membrane Fuel Cells

Composite Nafion-based membranes containing nanosize and submicrometer-size titanium dioxide (TiO2) and tin dioxide (SnO2) were fabricated by recasting from Nafion solution. Proton exchange membrane fuel cell tests were conducted using these composite membranes at 80 degrees C over a relative humidity (RH) range between 25 and 100%, using high-purity H-2 and O-2 gases. Cell tests were also conducted at 120 degrees C and low RH. Composite membranes containing nano-TiO2 and SnO2 fillers showed a significant performance improvement over Nafion membranes without fillers and over composite membranes containing submicrometer-size TiO2 and SnO2 powders. The relative performance improvement was greater at higher temperature and low RH. The particle size (surface area) of the nanopowders plays an important role in water retention and performance of composite membranes at 80 and 120 degrees C. The performance of SnO2 composite membranes was slightly better than TiO2 composite membranes for the same operating conditions. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.2994079] All rights reserved.