THE INTERACTION OF POTASSIUM SUBMONOLAYERS ADSORBED ON PT(111) WITH OXYGEN AND THE ADSORPTION OF ETHYLENE ON THE RESULTING MODIFIED SURFACES - A TDS AND UPS STUDY

UPS shows that K atoms deposited on Pt(111) in the submonolayer range strongly interact with oxygen molecules. At 300 K, oxygen molecules dissociate. Oxygen atoms either attach to potassium atoms or lead to K2O. At 95 K, depending on the experimental conditions (exposure and pressure), potassium peroxide or potassium superoxide, as majority species, form. TDS as well as UPS indicate that on these surfaces ethylene is pi-bonded as on Pt(111) surfaces, partially covered with K atoms. No ethylene adsorption occurs on surfaces fully covered with oxygen atoms or oxides. Ethylene adsorption therefore occurs on the clean part of the sample and is disturbed by the presence of various species of potassium attached to oxygen.