Engineering the structure defects of ceria-zirconia-praseodymia solid solutions for diesel soot catalytic elimination

Abstract

Creating structure defects in ceria-based solid solution catalysts is a crucial yet challenging task. Herein, urea-assisted synthesis strategy was designed for ceria-zirconia-praseodymia catalyst (CeZrPrO_x) to create lattice defects; its effects on catalyst structure, physical-chemical properties and catalytic diesel soot purification activity were systematically investigated. Raman and X-ray photoelectron spectroscopy (XPS) findings indicate that the urea-assisted synthesized catalyst (CeZrPrO_x-U) has remarkably more Ce³⁺ proportion (structure defects), oxygen vacancies and surface reactive oxygen species (O₂^2- and O^2-). Temperature-programmed reduction by hydrogen (H₂-TPR) and temperature-programmed desorption by oxygen (O₂-TPD) results further prove that the oxygen migration of the CeZrPrO_x-U is definitely enhanced. Compared to the conventional CeZrPrO_x catalyst, the bulk lattice oxygen of the CeZrPrO_x-U can be migrated to the surface to generate surface reactive oxygen species more easily. As a consequence, the prepared CeZrPrO_x-U catalyst exhibits obviously better catalytic diesel soot purification activity. Therefore, this study suggests that engineering the structure defects in CeZrPrO_x catalyst is an effective approach to improve physical-chemical properties and enhance the soot catalytic elimination activity of the catalyst.