Correlating Catalytic Methanol Oxidation with the Structure and Oxidation State of Size-Selected Pt Nanoparticles

We have investigated the structure and chemical state of size-selected platinum nanoparticles (NPs) prepared by micelle encapsulation and supported on γ-Al 2 O 3 during the oxidation of methanol under oxygen-rich reaction conditions following both oxidative and reductive pretreatments. X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS) spectroscopy measurements reveal that in both cases, the catalyst is substantially oxidized under reaction conditions at room temperature and becomes partially reduced when the reactor temperature is raised to 50 °C. Reactivity tests show that at low temperatures, the preoxidized catalyst, in which a larger degree of oxidation was observed, is more active than the prereduced catalyst. We conclude that the differences in reactivity can be linked to the formation and stabilization of distinct active oxide species during the pretreatment.