The Effect of Ruthenium on the Binding of CO, H2, and H2O on Pt(110)

Abstract

Ruthenium is known to improve the CO tolerance of platinum based fuel cell catalysts, but the mechanism is unclear. Some investigators believe that the main role of ruthenium is to dissociate water, and thereby provide a faster route for the oxidation of CO. Other investigators believe that ruthenium changes the electronic structure of platinum, in a way that lowers the binding energy of the CO and thereby promotes easy reaction. In this study, we have used TPD to measure the magnitude of the two effects in UHV. When we deposit 0.25 monolayers of ruthenium on Pt(110), we find that the adsorption properties of the surface change substantially. The surface only adsorbs about half as much CO and H2. The sticking probability of water is also reduced. The β2 hydrogen peak disappears, whereas the α1 CO peak is attenuated by a factor of 2. The binding energy of the α1 CO decreases from 31 to 29 kcal/mol when ruthenium is added to the surface, whereas the binding energy of the α2 CO decreases from 25 to 23 kcal/m...