Photographic production of metal nano-particles for fuel cell electrodes

A photographic Pt printing process has been used to prepare catalysts for fuel cell applications. Ferric oxalate was used as a UV sensitizer, absorbing UV energy and converting Fe3+ to Fe2+, which then reduces metal catalyst ions, such as Pt or Pd ions to metals in the presence of a developer, such as ammonium citrate. Transmission electron microscope (TEM) and scanning electron microscope (SEM) studies revealed that Pt particles smaller than 5 nm were formed, however, the particles tended to aggregate and form clusters up to 300 nm. A deposition efficiency of 16% was obtained when Pt was printed on Nafion membranes. The catalytic performance of the photo-printed Pt was evaluated using a single H2 fuel cell. The mass-specific electrochemical area of the catalyst, H2 crossover rate through the Pt-printed membrane and the membrane resistance were measured. At 60 °C, a peak power density of 75 mW cm−2 was obtained with a MEA consisting of photo-printed Pt (0.12 mg cm−2) on a Nafion membrane as the catalyst. Cyclic voltammetry measurements in solutions containing methanol or formic acid showed that a mass-specific methanol oxidation current of 197 mA mg−1 Pt could be achieved and that the co-deposition of Pd with Pt lowered the formic acid oxidation potential in addition to reducing the formation of the “poisonous” intermediate COads.