Tuning the oxidation of carbon monoxide using nanoassembled model catalysts

Abstract

While the oxidation of CO has long been considered to be structure insensitive, nano-assembled model catalysts consisting of size-selected metal clusters (Au n , Pt n , Pd n , and Rh n , n=1–20), supported on thin MgO(1 0 0) films, reveal distinct size-effects. When adding a single Pt atom to Pt 14, platinum clusters increase their reactivity by a factor of three. Rh 20 shows the highest reactivity of all the investigated clusters, oxidizing about 13 CO molecules per cluster at 350 K. While F-centers on MgO films transform Au 8 from an inert to an active catalyst, the reactivity of Pd 8 is not suppressed when deposited on defect-poor films. These different catalytic properties are rationalized within simple frontier orbital models, whereas for Au 8 the reaction mechanism for the low temperature oxidation of CO is elucidated within first-principle calculations.