H-CO INTERACTIONS ON THE TERRACES AND STEP EDGES OF A STEPPED PT SURFACE

We have studied coadsorbed CO and H on the stepped Pt(335) surface wit h electron energy loss spectroscopy and temperature-programmed desorpt ion. Radically different coadsorption behavior is found on the step ed ges and the terraces. Along the edge coadsorbed H strongly affects CO' s vibrational spectrum, shifting CO from atop to bridge sites and enha ncing the cross section of bridge CO. On the terrace coadsorbed H has virtually no effect on CO's spectrum, even at very high H coverage. Bo th of these behaviors differ from the interactions observed on Pt(111) . Possible explanations are discussed.