Increasing the Number of Oxygen Vacancies on TiO2 by Doping with Iron Increases the Activity of Supported Gold for CO Oxidation

The addition of iron to high‐area TiO2 (Degussa P25, a mixture of anatase and rutile) increases the number of oxygen defect sites that react with O2 to form peroxide and superoxide species. In the presence of gold nanoclusters on the TiO2 surface, the superoxide species become highly reactive, and the activity of the supported gold catalyst for CO oxidation is approximately twice that of the most active comparable catalysts described in the literature. Images of the catalyst obtained by scanning transmission electron microscopy combined with spectra of the catalyst measured in the working state (Raman, extended X‐ray absorption fine structure, and X‐ray absorption near‐edge structure) indicate strong interactions of gold with the support and the presence of iron near the interfaces between the gold clusters and the TiO2 support. The high activity of the catalysts is attributed to the presence of defects in these sites that activate oxygen. Enhanced activity of gold supported on Fe‐modified TiO2 as a catalyst in CO oxidation results from Fe‐promoted formation of oxygen vacancies which activate O2 by forming superoxide species that react with CO adsorbed on gold clusters to form CO2 (see picture) according to studies by in situ Raman and X‐ray spectroscopy and electron microscopy.