CO oxidation activity of gold catalysts supported on various oxides and their improvement by inclusion of an iron component

A number of oxide-supported gold catalysts have been prepared by deposition–precipitation, with variation of the pH over a wide range, the optimum pH for high activity being 9 for TiO2, 7.5 for Fe2O3, and 7 for SnO2 and CeO2. Whereas the activity shown by Au/TiO2 and Au/Fe2O3 decreased linearly with time, Au/CeO2 and Au/SnO2 underwent an initial major deactivation. Addition of iron in the preparation lowered the rate of deactivation when TiO2, SnO2 and CeO2 were used as supports, and imparted activity when as with Bi2O3 it was previously lacking. XPS revealed the existence of a broad multi-state iron-containing region, and TEM and STEM/EDX indicated that small gold particles (1.5–4 nm) were partly in contact with it. Improved stability is therefore due to gold particles being in contact with an iron phase such as FeO(OH); calcination removed the stabilisation.