CHEMISORPTION AND THERMAL-DECOMPOSITION OF ETHYLENE ON A PD(110)(1X2)-CS SURFACE - ELECTRON-ENERGY LOSS SPECTROSCOPY AND THERMAL-DESORPTION STUDIES

The adsorbed state of ethylene on the Pd(110)(1×2)-Cs surface and its thermal decomposition have been studied by the use of high-resolution electron energy loss spectroscopy and thermal desorption spectroscopy. For a small exposure (0.1 langmuir) at 90 K, ethylene is π-bonded to the Pd(110)(1 × 2)-Cs surface. For a large exposure (2 langmuirs), a small amount of physisorbed ethylene exists in addition to π-bonded ethylene. The saturation coverage corresponds to 0.23 C2H4 molecules per Pd atom of the unreconstructed Pd(110) surface. The physisorbed ethylene is desorbed by heating to 110 K. A part of the π-bonded ethylene is desorbed intact at 200 K, and additionally at 270 K by a recombinative process. By heating to 300 K, the residual C2H4 admolecules are decomposed, and methylidyne (CH) species are formed. Only carbon adatoms remain on the Pd(110)(1×2)-Cs surface by heating to 500 K. These results are compared with those for the Pd(110) clean surface, and the effects of Cs adatoms on the surface reactions are discussed. © 1990 American Chemical Society.