Reduction of High Surface Area CeO2−ZrO2 Mixed Oxides

• Published in: The journal of physical chemistry. B 2000-10, Vol.104 (39), p.9186-9194
• Main Authors: Daturi, Marco, Finocchio, Elisabetta, Binet, Claude, Lavalley, Jean-Claude, Fally, Fabienne, Perrichon, Vincent, Vidal, Hilario, Hickey, Neal, Kašpar, Jan
• Format: Article
• Language: English
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp000670r

The objective of this study was to examine the mechanism of the reduction by hydrogen of ceria−zirconia (CZ) mixed oxides having a high BET surface area (100 m2 g-1). Three methods were used in parallel to assess the Ce3+ content, the surface and bulk oxygen vacancy concentrations, and the resulting oxygen storage capacity (OSC):  temperature programmed reduction, Fourier transform infrared (FT-IR) measurements of methanol adsorbed on the reduced surfaces, and a Faraday microbalance to determine the magnetic susceptibility of the reduced oxides. The three methods conclude that the introduction of zirconium into the ceria lattice has a positive influence on the OSC. Compared to pure ceria, the CZ mixed oxides exhibit better redox properties, with a lower temperature of initial reduction and a higher reduction percentage for all compositions. The reducibility increases with the zirconium 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 samples oxidizes them almost completely. However, the FT-IR results underline the differing behavior of ceria for the distinct surface and bulk reduction processes.