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Abstract

Recent experimental and theoretical work on the CO oxidation reaction at "ruthenium" catalysts provides intriguing insight into the microscopic origins behind the frequently discussed pressure and materials gap between studies performed in ultra-high vacuum (UHV) and under realistic pressure conditions. Focusing on the Ru(0001) model catalyst, the considered system has, in fact, two important components to this issue. At first, an oxygen-rich environment changes the material from Ru to RuO₂. Thus, earlier ambient pressure studies on "ruthenium" catalysts were actually looking at an oxide film formed at the surface. Second, even after RuO₂ has been formed, the surface composition varies greatly with pressure: also, on the formed RuO₂(110) there is a low-pressure surface phase that is routinely studied in UHV, but has little in common with the catalytically active situation.