Abstract
The morphology of Pt Cu surface alloys is studied by CO and Xe adsorption/desorption after annealing Pt films on a Cu(111) substrate at temperatures above 500 K. The topmost layer consists of dispersed Pt atoms in a Cu matrix. The Xe desorption peak maximum proportionally shifts to lower temperatures with decreasing Pt surface concentration. Accordingly, Xe TDS can be used to determine the Pt concentration in the surface. The adsorption properties of CO on the thus prepared PtCu surfaces have been studied by thermal desorption spectroscopy (TDS), high resolution electron energy loss spectroscopy (HREELS), and work function change measurements (Δ∅). Pt, Cu, and mixed adsorption sites can be distinguished with TDS. HREELS shows that CO on top of Pt is the prevalent adsorbed species. Both HREELS and Δ∅ show that the amount of bridge bonded CO has a minimum at a surface concentration of 20% Pt.
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