Preparation and Physical and Electrochemical Properties of Carbon-Supported Pt-Ru (Pt-Ru/C)
Samples Using the Polygonal Barrel-Sputtering Method
J. Phys. Chem. C 2008, 112, 1479 -1492
Mitsuhiro Inoue*, Hiroshi Shingen**, Tomohito Kitami**, Satoshi akamaru*,
akira Taguchi*, Yasuhisa Kawamoto**, Akio Tada**, Kazuhiko Ohtawa**,
Kanji Ohba**, Masao Matsuyama*, Kuniaki Watanabe*, Iwao Tsubone*, and Takayuki Abe*
*Hydrogen Isotope Research Center, University of Toyama, Gofuku3190,Toyama 930-8555,Japan
**Nippon Pillar Packing Corporation, 541-1, Uchiba, Shimouchigami, Sanda, Hyogo 669-1333, Japan
Abstract
Carbon-supported Pt-Ru alloy (Pt-Ru /C) catalysts were prepared using the "polygonal barrel-sputtering method".
From the preparation of a Pt-Ru alloy with Pt/Ru = ca. 50:50 atom % on a glass plate as support, the optimum sputtering conditions were
an ar gas pressure of 0.9-0.7 Pa and room temperature. The amount of the sputtered Pt-Ru alloy was controlled by changing the ac power and
the sputtering time. Subsequently, the Pt-Ru/C samples were prepared under the given optimum conditions. The Pt-Ru alloy was dispersed
extensively in the form of nanoparticles on a carbon support. For the ac power levels of 130, 100, and 50 W, the size distributions were
narrower when the ac power was lowered. The respective average particle sizes were 4.1 nm (130 W), 3.3 nm (100 W), and 2.2 nm (50 W).
In the case of 30 W, however, the size distribution and the average particle size were almost identical to those for 50 W. In addition,
when the Pt-Ru/C samples were prepared by changing the sputtering time, only the dispersion density of the alloy nanoparticles increased
in the Pt and the Ru deposited without changing the particle size. The atomic ratios of Pt and Ru in individual Pt-Ru alloy nanoparticles
for the prepared samples were similar to the sputtering ratio and homogeneous compared with those for the commercially available samples.
With regard to the electrochemical properties for the prepared samples, the hydrodynamic voltammograms for H2 oxidation were identical to
that of the commercially available sample. However, for CO oxidation, the peak shapes and the peak potentials for the prepared samples were
sharper and ca. 20 mV lower than those for the commercially available samples, due to the uniform Pt and Ru atomic ratios of the individual
alloy particles for the prepared samples. The coulomb charges of the CO oxidation reaction per amount of Pt and Ru for the prepared samples
increased linearly in the reversed average particle sizes, while on the other hand, the charges for the commercially available samples were
not proportional to the reversed sizes. This shows that the Pt-Ru alloy for the prepared samples was more efficiently utilized for
electrochemical reactions rather than were the commercial ones. In addition, the cell performances for the alloy loading of 0.08 or 0.02
mg/cm2 using the prepared Pt-Ru /C samples were similar to those for 0.50 mg/cm2 using the commercially available sample.