CO chemisorption on the [111] and [100] oriented single crystal surfaces of the alloy CoPt 3

Abstract

In a previous study, it was shown that surfaces of both the [111] and [100] oriented single crystals of COPt 3 have a “sandwich” structure having an outermost atomic layer that is essentially pure Pt and a second layer enriched in Co (with respect to the bulk). In the present work, we report a study of the energetics of carbon monoxide chemisorption on these surfaces and compare the results with our previous study of carbon monoxide adsorption on Pt 3Ti surfaces. A surprising similarity in the activation energy for desorption of carbon monoxide from Pt sites on both the COPt 3 and the Pt 3Ti surfaces was found, with the adsorption energy being substantially lower on the alloy surfaces than on the pure Pt surfaces of the same orientation. Since the COPt 3 surfaces have a pure Pt top layer, it appears that the intermetallic bonding between Co in the second layer and Pt in the top layer changes the electronic states available for the bonding of carbon monoxide to the surface.