Enhancement of oxygen storage capacity by reductive treatment of Al2O3 and CeO2–ZrO2 solid solution nanocomposite

Abstract

Oxygen storage capacity (OSC) of CeO2–ZrO2 solid solution, CexZr(1−x)O4, is one of the most contributing factors to control the performance of an automotive catalyst. To improve the OSC, heat treatments were employed on a nanoscaled composite of Al2O3 and CeZrO4 (ACZ). Reductive treatments from 700 to 1000°C significantly improved the complete oxygen storage capacity (OSC-c) of ACZ. In particular, the OSC-c measured at 300°C reached the theoretical maximum with a sufficient specific surface area (SSA) (35m2/g) after reductive treatment at 1000°C. The introduced Al2O3 facilitated the regular rearrangement of Ce and Zr ions in CeZrO4 as well as helped in maintaining the sufficient SSA. Reductive treatments also enhanced the oxygen release rate (OSC-r); however, the OSC-r variation against the evaluation temperature and the reduction temperature differed from that of OSC-c. OSC-r measured below 200°C reached its maximum against the reduction temperature at 800°C, while those evaluated at 300°C increased with the reduction temperature in the same manner as OSC-c.