Reduction of high surface area CeO2-ZrO2 mixed oxides

The objective of this study was to examine the mechanism of the reduction b y hydrogen of ceria-zirconia (CZ) mixed oxides having a high BET surface ar ea (100 m(2) g(-1)). Three methods were used in parallel to assess the Ce3 content, the surface and bulk oxygen vacancy concentrations, and the resul ting oxygen storage capacity (OSC): temperature programmed reduction, Fouri er transform infrared (FT-IR) measurements of methanol adsorbed on the redu ced surfaces, and a Faraday microbalance to determine the magnetic suscepti bility of the reduced oxides. The three methods conclude that the introduct ion of zirconium into the ceria lattice has a positive influence on the OSC . Compared to pure ceria, the CZ mixed oxides exhibit better redox properti es, with a lower temperature of initial reduction and a higher reduction pe rcentage for all compositions. The reducibility increases with the zirconiu m content, however the OSC per gram of solid is practically the same for Zr contents between 20% and 50%. The reduction process very rapidly involves the bulk, but a treatment at room temperature under oxygen of the reduced s amples oxidizes them almost completely. However, the FT-IR results underlin e the differing behavior of ceria for the distinct surface and bulk reducti on processes.