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

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 (T-50) over which is 25 degrees 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 degrees C lower of T50 is detected over the aged CZAN7 (1000 degrees C/4h) than its fresh counterpart (600 degrees 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.