Redox behavior of CeO2-ZrO2 mixed oxides I. Influence of redox treatments on high surface area catalysts

Redox and textural/structural properties of high surface area ceria-zirconi a mixed oxides with composition ranging from 0 to 85 mol% of ZrO2, have bee n studied using Raman spectroscopy, X-ray diffraction, textural characteriz ation, magnetic susceptibility measurements, temperature-programmed reducti on and oxidation, oxygen storage and buffering capacity measurements. Speci al attention was given to the effects of aging under redox conditions. Correlation between chemical composition, textural, structural and redox pr operties of the oxides is reported. While for pure ceria almost no reducibi lity occurs below 773 K, mixed oxides, independently of their composition, exhibit an oxygen storage and buffering capacity at low temperature, which remains stable even after several oxidation/reduction cycles. This improvem ent with respect to CeO2 is remarkably high in the oxides with high zirconi a content and is not affected by worsening of textural properties induced b y redox-aging. Phase transformation and/or structural modification are dete cted as a consequence of the redox treatments, which could be at the origin of such effects. (C) 2000 Elsevier Science B.V. All rights reserved.