Deuterium-Oxygen Reaction on Pt(111) Catalysis by Defects
Because of the simplicity of the reactants and products, the hydrogen-oxygen reaction on Pt(lll) was believed to be an ideal model system for investigating chemical reactions on single crystal surfaces. However, in spite of the large number of studies1–6 (and references there in), a clear picture of the mechanism of the reaction has not yet emerged. The main reason for this appears to be that the role of defects has been ignored. We have shown previously that the kinetics of the hydrogen-oxygen reaction is sensitive to the presence of atomic steps3. However, this effect could still not explain the discrepencies reported in the literature. More recently, we found that the reaction is also sensitive to the presence of other defects, even at concentrations of 10-3 or below. We propose that these defects, which are very efficient in catalyzing the hydrogen-oxygen reaction, are kinks in atomic steps. Here we present additional evidence for this reaction mechanism and we will show that the observed kinetics of the reaction can be explained, at least qualitatively, by assuming that the reaction takes place exclusively at these reactive kink sites for surface temperatures around 400 K.
KeywordsAtomic Step Hydrogen Excess Sticking Probability Oxygen Coverage Step Site
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