Abstract

Thermal and chemical treatment of metallo-organic chemical vapor deposition (MOCVD)-prepared Rh and Pd model catalysts, supported on TiO2{110}, lead to the formation of carbon residues that are oxidized to CO at elevated temperatures. These processes are metal, metal precursor, and surface- treatment dependent. In the absence of surface Cl, Rh precursors exhibit surface carbon oxidation, at T > 775 K. In the case of Pd this is not seen until T > 825 K and some carbon is always found to remain. Room-temperature reduction of the model catalysts using hydrogen progressively lowers the temperature of carbon oxidation. However, reduction of a Cl-containing system dramatically promotes CO oxidation/Ar expulsion in a manner that is kinetically distinct from that observed in the absence of Cl. These observations are discussed in terms of the mobility of surface oxygen species on TiO2{110}, metal−support interactions, and the effect of Cl incorporation into the TiO2 substrate.

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