Abstract
Dehydrogenation and oxidation of methanol has been studied on well-ordered Pt(111), vicinal Pt(111), and Pt(111)/Ru in alkaline media. Multiple mechanisms of promotion have been identified. Steps with (110) orientation promote methanol dehydrogenation through a geometric effect, while they promote CO oxidation through a change in electronic structure. Adsorbed Ru promotes methanol dehydrogenation through two distinct electronic (ligand) effects: it increases the intrinsic activity of nearby Pt sites for methanol dehydrogenation, and it decreases the local CO coverage at the active sites even when the overall CO coverage is high. Ru also promotes methanol oxidation through a ligand effect on CO oxidation. The bifunctional effect of Ru is concluded to be much weaker in alkaline media than in acidic media. STM imaging confirms the stability of adsorbed Ru even during extended potential cycling and oxidizing treatments, demonstrating the promising characteristics of Pt/Ru surfaces for fuel cells.
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