Author/Authors :
Regine Streber، نويسنده , , R. and Papp، نويسنده , , C. and Lorenz، نويسنده , , M.P.A. and Bayer، نويسنده , , A. and Denecke، نويسنده , , R. and Steinrück، نويسنده , , H.-P.، نويسنده ,
Abstract :
We studied the influence of preadsorbed sulfur on the adsorption of CO on Pt(3 5 5) and Pt(3 2 2) by in situ X-ray photoelectron spectroscopy. At low temperatures, no adsorption of CO at steps is found, indicating a passivation by sulfur. Upon heating, population of step sites with CO occurs. This behavior is attributed to a kinetic passivation of the steps by sulfur at low temperatures, which is lifted upon heating. The characteristic transition temperatures of 185 K for Pt(3 5 5) and 240 K for Pt(3 2 2) are significantly different, due to a higher activation barrier for the CO/S site exchange process for Pt(3 2 2).
