The morphology and thermal stability of Pt particles deposited on Fe 3 O 4 (111) films were studied by scanning tunneling microscopy (STM) and temperature programmed desorption of CO. Vacuum annealing at temperatures above 800 K led to significant Pt sintering that reduced CO uptake to a much higher extent than the Pt surface area. A similar effect on CO adsorption was observed after mild oxidation−reduction treatment at 500 K. The results are rationalized in terms of the strong metal−support interaction between Pt and Fe 3 O 4, whereby the Pt particles were encapsulated by a FeO (111) monolayer film as shown by STM. The high adhesion energy between Pt and iron oxides derived from STM data is suggested to be the key factor for encapsulation.
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Qin et al. (2008) studied this question.
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