Facile synthesis of ceria-zirconia solid solutions with cubic-tetragonal interfaces and their enhanced catalytic performance in diesel soot oxidation

The rational design of a catalyst interface is crucial for the improvement of catalytic performance. Here, a CeO2-ZrO2 solid solution catalyst with cubic-tetragonal interfaces, CeO2-ZrO2(C-T), was synthesized using a solvothermal method. The catalytic performance of the prepared CeO2-ZrO2(C-T) catalyst in soot oxidation was compared with that of the current commercial CeZrLaPrOx and CeO2-ZrO2 soot oxidation catalysts; meanwhile, the catalysts were characterized systematically. X-ray diffraction and Raman spectroscopy results imply that cubic and tetragonal structures coexist, and the amounts of these phases are approximately equal (C/T = 41/59) in the synthesized CeO2-ZrO2(C-T) catalyst. Transmission electron microscopy images clearly demonstrate the presence of many cubic-tetragonal interfaces in the CeO2-ZrO2(C-T) catalyst. The prepared CeO2-ZrO2(C-T) catalyst has markedly better catalytic activity for soot oxidation than the commercial CeO2-ZrO2-based catalysts. This result is influenced by the existence of cubic-tetragonal interfaces in CeO2-ZrO2(C-T). X-ray photoelectron spectroscopy and oxygen temperature-programmed desorption results further indicate that the cubic-tetragonal interfaces in the synthesized CeO2-ZrO2(C-T) catalyst promote the production of structural defects (oxygen vacancies) and the release of surface lattice oxygen in the CeO2-ZrO2 solid solutions. The oxygen vacancies play a key role in the activation of gaseous oxygen to form active oxygen species (O-x species) for soot oxidation, and the lattice oxygen atoms also play a favorable role in the creation of highly active O-x(-) species. The surface-active O-x(-) species created by the surface lattice oxygen can immediately contact the soot and then rapidly promote the oxidation reaction. Hence, this work suggests that the cubic-tetragonal interfaces present in CeO2-ZrO2 solid solutions are also a relevant factor contributing to their excellent catalytic performance in diesel soot oxidation. (C) 2019 Elsevier Inc. All rights reserved.