High utilization of Pt nanocatalysts fabricated using a high-pressure sputtering technique

Pt nanocatalysts formed on a gas diffusion layer substrate for use in proton exchange membrane fuel cells were fabricated by using a high-pressure sputtering technique in a gaseous mixture of Ar and He. Rather than the dense film deposited by conventional sputtering techniques, the resulting structure was comprised of a porous Pt nanocatalyst layer with an average particle size of 8.9 nm. The porous Pt nanocatalysts were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray absorption near edge spectroscopy. Compared with the dense Pt catalyst layer, the electrochemical activated surface of the porous Pt nanocatalyst layer, measured using cyclic voltammetry, was enhanced about 250%. Polarization characteristics of the membrane electrode assembly, which utilized the porous Pt nanocatalyst layer in the proton exchange membrane fuel cells, showed that the maximum power density per unit area increased with an increase in the sputtering pressure. The high performance of Pt nanocatalysts fabricated at a sputtering pressure of 200 mTorr (Ar/He = 1) was due to miniaturization of the Pt particles and formation of the porous catalyst layer. (C) 2007 Elsevier B.V. All rights reserved.