Low-Temperature Operation of CeO₂-ZrO₂-Based Oxygen Storage Materials

Abstract

CeO 2 -ZrO 2 -based oxides are widely used in automobiles to remove harmful components in exhaust gas. Ce 0.5 Zr 0.5 O 2 (CZ55) shows an excellent oxygen storage capacity (OSC); however, it is difficult to keep its OSC at low temperatures such as 400 °C. This is because of limited oxygen transport in this temperature range. Our previous research revealed that the addition of CoFe 2 O 4 (CFO) was effective to improve its OSC at low temperature. The purpose of this study is to clarify the role of CFO on the phases present and OSC properties including surface kinetics of CZ55. CFO-added CZ55 was prepared by Pechini and solid-state reaction techniques. OSC was evaluated by thermogravimetric analysis (TGA) at 400°C in 5%H 2 -Ar and synthetic air. Surface exchange reaction rates were analyzed by a pulse isotope exchange (PIE) technique. CFO was found to be soluble in CZ55 up to 5 vol%. The 5 vol%CFO-added CZ55 showed an excellent OSC at 400 °C. The activation energy of surface exchange kinetics was also affected by CFO addition.