(5ba) The Development and Reactivity of Oxide Phases on Pd(111) Utilizing Gas Phase Oxygen Atom Beams in Ultra High Vacuum

Palladium oxide is an excellent catalyst for the oxidation of hydrocarbons and carbon monoxide under oxygen-rich conditions. However, the fundamental mechanisms governing oxide growth and reactivity still remain unclear due to difficulties associated with oxidizing palladium under the ultra high vacuum conditions necessary for most surface analytical techniques. Over the past two years we have made strides in elucidating the mechanisms for the growth and reactivity of palladium oxide by utilizing gas phase oxygen atoms beams to simulate high pressure oxidizing environments while operating under clean ultra high vacuum conditions. We present our recent findings concerning the growth and properties of palladium oxide on Pd(111) in addition to studying the effects of gas phase oxygen atom flux and substrate temperature on oxide growth. Notably, we have found that low temperature oxidation of Pd(111) with gas phase oxygen atoms enables the formation of a single crystalline PdO(101) thin film which has never been observed using molecular oxidants. This ability to generate PdO(101) has enabled us to be the first to study the interaction of molecular oxygen, water, hydrogen, and carbon monoxide with a single crystalline facet of PdO which we will also present.