The thermal stability of wet-chemically prepared Cu/SiO 2 model catalysts containing nanometer-sized Cu particles on silica model supports was studied upon heating in hydrogen and ultrahigh vacuum. The surface and interface phenomena that occur are determined by the metal−support interactions. Heating in hydrogen results in a reduction of the metal−support interaction and sintering occurs via Cu particle migration at 350 °C. Annealing in ultrahigh vacuum up to 620 °C does not result in sintering of the Cu particles. When a 5 nm thin SiO 2 layer on top of a Si(100) substrate is used as SiO 2 model support, interdiffusion of Cu into the Si substrate takes place. For a 400−500 nm thick SiO 2 layer, Cu silicide islands are formed by reaction between Cu and SiO 2, which can be regenerated by exposure to air at room temperature for several hours. The importance of the preparation procedure for the strength of the metal−support interaction is discussed. This paper shows that the use of model catalysts to study surface and interface phenomena is relevant for technical heterogeneous metal catalysis.
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Oetelaar et al. (1998) studied this question.