Single–atom Ir1 supported on rutile TiO2 for excellent selective catalytic oxidation of ammonia

Gaseous ammonia (NH 3 ) in the atmosphere is potentially harmful to both human health and the environment. The selective catalytic oxidation of NH 3 (termed as NH 3 –SCO) into N 2 and H 2 O is a promising method for decreasing NH 3 emissions. A highly efficient catalyst is required for controlling NH 3 emissions by this method in practice. In this study, we prepared Ir/TiO 2 catalysts using different crystal structures of TiO 2 (rutile, P25 or anatase) as supports by a simple impregnation method and evaluated their performance in the NH 3 –SCO. We found that the Ir/TiO 2 –R (rutile) catalyst performed better than the Ir/TiO 2 –P25 (mixed–phase) and Ir/TiO 2 –A (anatase) catalyst. High–angle annular dark–field images of the aberration–corrected scanning transmission electron microscopy revealed that the Ir species were mainly atomically dispersed on the TiO 2 support in Ir/TiO 2 –R with 1 wt% Ir loading, whereas the Ir species agglomerated to form clusters or nanoparticles in Ir/TiO 2 –P25 and Ir/TiO 2 –A. The combined results of X–ray absorption fine structure, H 2 –temperature–programmed reduction, and in situ diffuse reflectance for infrared Fourier Transform spectroscopy studies suggested that atomically dispersed Ir species had stronger electronic metal–support interaction with rutile TiO 2 , which resulted in easier to adsorb and activate O 2 at the interface and thus, better low–temperature activity of the Ir/TiO 2 –R catalyst.