Adsorption and thermal behaviour of ethane and ethene on oxygen precovered Ni(111)

Ni as well as NiO are widely-used catalysts in chemical industry. To understand the adsorption and reaction properties of small hydrocarbons on such surfaces we studied ethane and ethene on clean and oxygen precovered Ni(111) by means of XPS using synchrotron radiation at BESSY II. The gases were dosed using a supersonic molecular beam; for C{sub 2}H{sub 6} this provided the kinetic energy required for the activated adsorption yielding adsorbed C{sub 2}H{sub 5}. On clean Ni(111) both C{sub 2}H{sub 5} and C{sub 2}H{sub 4} give rise to two separate C 1s peaks, indicative of a different local environment for the two C atoms in both cases. In contrast, on oxygen precovered Ni(111) only one C 1s peak is observed after exposing the surface to C{sub 2}H{sub 4}, and for C{sub 2}H{sub 5} the peak separation is strongly reduced, indicating major changes in the adsorption geometries. Furthermore, we also studied the thermal evolution of the adsorbed hydrocarbons and found significant differences between oxygen free and oxygen precovered Ni(111).