Two new methods for monolayer-to-multileyer Pt deposition are presented. One
involves Pt deposition by the replacement of an UPD metal monolayer on an
electrode surface and the other the spontaneous deposition of Pt on Ru. The
first method, exemplified by the replacement of a Cu monolayer on a Au(111)
surface, occurs as a spontaneous irreversible redox reaction in which the Cu
monolayer is oxidized by Pt cations, which are reduced and simultaneously
deposited. The second method is illustrated by the deposition of Pt on a
Ru(0001) surface and on carbon-supported Ru nanoparticles. This deposition
takes place upon immersion of a UHV-prepared Ru(0001) crystal or Ru
nanoparticles, reduced in H2, in a solution containing PtCl6 2- ions. The
oxidation of Ru to RuOH by a local cell mechanism appears to be coupled with
Pt deposition. This method facilitates the design of active Pt-Ru catalysts
with ultimately low Pt loadings. Only a quarter of a monolayer of Pt on Ru
nanoparticles yields an electrocatalyst with higher activity and CO
tolerance for H2/CO oxidation than commercial Pt-Ru alloy electrocatalysts
with considerably higher Pt loadings.