Gold nanoparticles: effect of treatment on structure and catalytic activity of Au/Fe2O3 catalyst prepared by co-precipitation

1 wt% Au/Fe2O3 catalyst was prepared by a co-precipitation method. The stru cture of the sample in the as prepared, oxidized and reduced states was inv estigated by means of X-ray photoelectron spectroscopy (XPS), transition el ectron microscopy (TEM), electron diffraction (ED) and X-ray diffraction (X RD). The structure of the samples after various treatments and their activi ty in the CO oxidation were compared. The results show the stability of the gold particle size during the treatments. However, after oxidation, a slig ht shift in the Au 4f binding energy towards lower values points to the for mation of an electron-rich state of the metallic gold particles compared to that revealed in the as prepared sample. Simultaneously, a goethite phase in the Fe2O3 support is present, which is not observed in the "as prepared" and reduced samples. In the reduced sample the presence of a crystalline m aghemite-c phase indicates a change in the support morphology. In the CO ox idation the oxidized sample shows the highest activity and it might be the result of the cooperative effect of goethite, FeO and the electron-rich met allic gold nanoparticles. We suggest that a structural transformation occur s along the gold/support perimeter during the treatments and we propose a p ossible mechanism for the effect of the oxidation treatment.