Infrared study of nitric oxide (NO) adsorption and conversion on CeO2-ZrO2 mixed oxide

An IR study of adsorption of NO- and CO-containing mixtures on a high-surface-area Rh/Ce0.5Zr0.5O2 mixed oxide is reported. At low temperatures, NO strongly interacts with surface oxygen. The presence of various NOx-containing species co-ordinated both to cerium and zirconium has been observed. The NOx storage capacity is mainly associated with the presence of zirconium sites. The extension of NOx storage strongly depends on the adsorption temperature, which is associated with the presence/absence of reactive surface oxygen species. Formation of N2O22- as adsorbed species appears to be a possible key step in the mechanism for conversion of NO at low temperature.