Abstract:

Gasoline soot particles pose a severe threat to the ecological environment and human health, but they can be potentially filtered out by using catalytic gasoline particulate filter (cGPF), whose core component is a catalyst coating. To develop more effective catalyst coatings with excellent activity, stability, and water resistance, a kind of composite oxide MnO_x/CeO₂-ZrO₂ was synthesized using different methods, and its soot oxidation performance was evaluated under low O₂ concentrations. Herein, MnO_x/CeO₂-ZrO₂ prepared by impregnation (abbreviated as MCZ-IM) exhibits a T₅₀ (temperature required for 50% soot conversion) of 329 ℃ in 1% O₂ and 370 ℃ in 0.5% O₂, displaying better comprehensive performance when compared to catalysts prepared by high-energy ball milling (abbreviated as MCZ-HB) and co-precipitation (abbreviated as MCZ-CP). Structure-activity relationship reveals that soot oxidation under low O₂ concentrations is weakly correlated with textural and structural properties, but strongly depends on the generation and migration of active oxygen species (AOS), especially superoxide (O₂^-) and peroxide (O₂^2-) anions, which are linked to redox properties, oxygen storage and release capacity, as well as amount of oxygen vacancies. The impregnation method enhances oxygen species adsorption, activation and desorption more effectively, endowing it with a more effective approach to enhancing AOS generation and mobility. Therefore, this study not only provides a preparation strategy for particulate matter oxidation catalysts applicable to actual operating conditions, but also offers insights into the migration of AOS at low O₂ concentrations.

Key words: MnO_x/CeO₂-ZrO₂, catalyst, soot, active oxygen species