Double-stable Ce-based oxide: Capturing atomic precious metals via Ostwald ripening for multicomponent three-way catalysts construction

Abstract

Precious metal catalysts have been widely used to catalyze various reactions, particularly three-way catalysts for automobile exhaust purification. Pt, Pd, and Rh, which are dispersed on Ce-based oxides that store and release oxygen, serve as the active center of a catalyst. However, methods to construct multifunctional three-way catalysts to maximize their efficiency and stabilize them are lacking. In this study, Ce-based oxides with a double-stable mode were synthesized to capture and stabilize the precious metals Pt and Rh migrated by Ostwald ripening (OR), and a multicomponent three-way catalyst was accurately synthesized, which showed good catalytic activity and thermal stability. The origin of Ce-based oxides with a dual-stable mode was studied by TEM, XRD, oxygen storage/release capacity and rate test, and XPS. AC-STEM, EXAFS, in situ diffuse reflectance Fourier transform infrared, and H2 temperature-programmed reduction studied the OR migration of precious metals and the composition change after aging. Results showed that in the lean/rich oxygen alternating shift atmosphere containing CO, the proportion of OR migration of Pt and Rh precious metals whose initial state is single atoms can reach 100 %. This discovery provides a basic understanding of the sintering mechanism of precious metals, which is of great importance for the development and industrial application of three-way catalysts.