The electrooxidation of carbon monoxide on ruthenium modified Pt(110)

The effect of adsorbed and incorporated (alloyed) sub-monolayers of Ru on P t(110) on the electrooxidation of CO has been investigated using UHV-electr ochemical transfer techniques. Overlayers of metal vapour deposited (MVD) R u were characterised using LEED, XPS and LEISS. Both adsorbed and incorpora ted Ru overlayers were prepared, the alloy layers formed by annealing in th e temperature range 400-1100 K. The reversible hydrogen adsorption characte ristics of Pt(110) were suppressed in the cyclic voltammetry when Ru was ad sorbed, incorporated in the top layer, or when absent from the top layer wh ere there was a significant concentration of Ru in the second/third layers. Surfaces exhibited significant redox behaviour in the double layer region (0.3-0.6 V) of Pt(110) also when ruthenium was present in the adsorbed or t op surface phases, but to a much lesser extent when incorporated in the sec ond/third layer. CO electrooxidation, however, was promoted primarily by Ru incorporated in the top layer. Cycling to potentials of 1.2 V resulted in facile oxidative dissolution of adsorbed Ru, but only slow dissolution of R u when incorporated in the top layer. The effect of cycling to 1.2 V on sur faces with negligible Ru in the top layer, but Ru in the second and third l ayers, was to modify the CO oxidation behaviour substantially, producing a significant coverage of a Pt(110)-Ru phase which promoted CO oxidation in a peak at 0.5 V. (C) 1998 Elsevier Science Ltd. All rights reserved.