Growth of ruthenium islands on Pt(hkl) electrodes obtained via repetitive spontaneous deposition

We have examined the ruthenium island growth on Pt(111), Pt(100), and Pt(110) surfaces resulting from repeated spontaneous depositions of ruthenium from a 1 mM RuCl3 in 0.1 M HClO4 solution. Scanning tunneling microscopy and cyclic voltammetry were used to characterize the multiple depositions. We found that the details of the island growth were strongly single-crystal substrate dependent. On Pt(111), after four depositions, approximately 30 35% of the surface is covered with large (2-12 nm) ruthenium islands of varying heights. About 65% of the islands surface is a monolayer high, while 25% consists of two ruthenium layers and 10% consists of three monolayers or higher. However, it was revealed via STM imaging, that on Pt(100) and Pu(110). the two and three dimensional growth of the islands is much lower, It was possible to obtain 40% coverage of ruthenium on Pt(100) with 92% of the island area a monolayer high, while the island size ranged from 0.5-4 nm. On Pt(110), the tendency to grow in three dimensions is even less, its 98% of the islands peppering the surface are a monolayer high. These results are discussed its they pertain to possible use of additive island-covered nanoparticles in methanol oxidation fuel cell catalysis. (C) 2002 Published by Elsevier Science B.V.