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Zusammenfassung:
The reducibility of iron oxide nanoparticles (NPs) supported over few-layer thick graphite upon annealing in hydrogen is investigated by near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS), near-edge X-ray absorption fine structure (NEXAFS), electron energy loss spectroscopy (EELS), and high resolution transmission electron microscopy (HR-TEM). It is found that the stability of the iron oxide NPs toward reduction is enhanced by the interaction with the graphene nanosheets, as compared to the bulk iron oxide. Post-annealing TEM micrographs reveal the existence of both core/shell and homogeneous iron oxide NPs, with the latter forming irregular trenches into the graphene sheets. EELS analysis and TEM images clearly demonstrate that the reducibility of iron oxide particles depends on the specific graphene site on which they are attached. Furthermore, we show that graphene etching can be mediated by iron oxide NPs at relatively mild reduction conditions.
