Reducibility Studies of Ceria, Ce0.85Zr0.15O2 (CZ) and Au/CZ Catalysts after Alkali Ion Doping: Impact on Activity in Oxidation of NO and CO

The aim of these studies was to perform thorough research on the influence of alkali metalions (Li, Na, K and Cs) on the properties of nanogold catalysts supported on ceria-zirconia. Theaddition of alkali metal ions onto CeO2further affected the reducibility, which was not noted forthe Zr-doped support (Ce0.85Zr0.15O2). Despite the substantial impact of alkali metal ions on thereducibility of ceria, the activity in CO oxidation did not change much. In contrast, they do nothave a large effect on the reducibility of Au/CZ but suppressed the activity of this system in COoxidation. The results show that for CO oxidation, the negative effect of potassium ions is greaterthan that of sodium, which corresponds to the shift in the Tmax of the reduction peak towards highertemperatures. The negative effect of Li+ and Cs+spans 50% CO conversion. The negative effect wasvisible for CO oxidation in both the model stream and the complex stream, which also containedhydrocarbons and NO. In the case of NO oxidation to NO2, two temperature regimes were observedfor Au + 0.3 at% K/CZ, namely in the temperature range below 350 oC; the effect of potassiumions was beneficial for NO oxidation, whereas at higher temperatures, the undoped gold catalystproduced more NO2.