Mo/W mixed oxide with Mo/W molar ratio 80/20 was prepared by precipitation of the hydrate from an aqueous solution of ammonium heptamolybdate and ammonium paratungstate, followed by decomposition at 723 K in oxygen flow. Morphological, structural and textural characterisation was carried out by XRD and SEM technique. FT-IR and UV-Vis-NIR spectra recorded after reducing treatments (vacuum, CO or CO/O2) at increasing temperatures showed the increase of a variety of broad absorptions both in the Vis-NIR and medium IR regions. These absorptions decreased in intensity after contact with oxidising atmospheres (O2 or NO2/O2) at increasing temperature, so that they are all assignable to electronic transitions related to oxygen defects.
Spectroscopic characterisation of defects on Mo/W mixed oxide
MORANDI, Sara;GHIOTTI, Giovanna;CHIORINO, Anna;
2004-01-01
Abstract
Mo/W mixed oxide with Mo/W molar ratio 80/20 was prepared by precipitation of the hydrate from an aqueous solution of ammonium heptamolybdate and ammonium paratungstate, followed by decomposition at 723 K in oxygen flow. Morphological, structural and textural characterisation was carried out by XRD and SEM technique. FT-IR and UV-Vis-NIR spectra recorded after reducing treatments (vacuum, CO or CO/O2) at increasing temperatures showed the increase of a variety of broad absorptions both in the Vis-NIR and medium IR regions. These absorptions decreased in intensity after contact with oxidising atmospheres (O2 or NO2/O2) at increasing temperature, so that they are all assignable to electronic transitions related to oxygen defects.
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