Bifunctional roles of Nd2O3 on improving the redox property of CeO2–ZrO2–Al2O3 materials

Abstract

A series of Nd2O3 was introduced into CeO2–ZrO2–Al2O3(CZA) materials to improve their redox property, and then their soot oxidation activities were characterized. Although Nd2O3 incorporation obviously decreased the specific surface area, 7 wt% Nd2O3 modified CZA (fresh CZAN7) also exhibited the best activity, the temperature for 50% soot conversion (T50) over which is 25 °C lower than that over fresh CZA due to the more surface oxygen vacancies and the faster mobility of oxygen species. It indicates that redox property of CZA plays a critical role than specific surface area in determining the soot oxidation activity. Meanwhile, it is interesting that 31 °C lower of T50 is detected over the aged CZAN7 (1000 °C/4h) than its fresh counterpart (600 °C/3h). Combined with the results of Powder X-ray diffraction (XRD), High-resolution transmission electron microscope (HRTEM) and Raman, a new sight about the bifunctional roles of Nd2O3 on improving the redox property of CZA has been put forward. Nd2O3 could directly incorporate into CeO2–ZrO2 lattice to form CeO2–ZrO2-Nd2O3 solid solution. Meanwhile, it could also regulate the distribution of Zr species and promote them incorporate into CeO2–ZrO2 lattice during thermal treatment. Then CZAN7 could exhibit more surface oxygen species, increased surface oxygen vacancies and better soot oxidation activity even being thermally aged.