The ESR Study of O2– Radical Anion Formation during Adsorption of an NO + O2 Mixture and O2 on ZrO2 and (0.1–2.0)% MoO3/ZrO2

The influence of conditions of the preliminary thermal treatment of ZrO2, ammonia and methanol adsorption, and MoO3 supporting on O2– formation during the adsorption of an NO + O2 mixture was studied. The interaction of O2– with different molecules was studied. Adsorbed ammonia and methanol, as well as supported Mo6+ ions, were shown to inhibit this reaction. The involvement of the Zr4+ and O2– Lewis sites in the reaction was concluded. The interaction of ammonia and methanol with the O2– radical anions changed the g tensor parameters and decreased the thermal stability of O2– in the case of methanol. O2– radical anions were formed on the reduced (0.1–2.0)% MoO3/ZrO2 samples during the interaction of O2 with the Mo5+ ions in the octahedral configuration. As in the case of O2– formation during NO + O2 adsorption on ZrO2, the radical anions were localized in the coordination spheres of the coordinately unsaturated Zr4+ ions. A change in the MoO3 content of the samples from 0.1 to 0.5% led to an increase in the amount of O2–, whereas a change from 0.5 to 2.0% led to a decrease in the O2– amount due to the screening of the Zr4+ ions by oxo complexes and polymolybdates.