Constructing nano-structure on silver/ceria-zirconia towards highly active and stable catalyst for soot oxidation

- Highly active Ag/Ce-Zr catalyst with 'Ag/Ce' structure was successfully synthesized.
- Precipitant can affect the size of Ag particles and alter Ag-Ce interaction.
- The optimal interaction was beneficial for the increase of superficial Ag+ species.
- The catalyst/soot contact for the Ag/Ce-Zr catalyst is expected to be enhanced.
- Ag/Ce-Zr catalyst was utilized five times without any appreciable loss of activity.

Different to Pt-based catalysts used in diesel particulate filter (DPF), Ag/CeO2-ZrO2 catalyst, whose main feature is a considerable amount of silver species exposed on the surface of catalyst, possesses outstanding soot oxidation performance even in loose contact mode and in the absence of NOx. The Ag/CeO2-ZrO2 catalyst with the special structure and Ag particle ranging from 17 to 35 nm is herein prepared by controlling precipitant, and its combustion temperature T10 and Tmax can be achieved as low as 254 °C and 280 °C in 5.0% H2O/4.8% O2/90.2% N2 and loose contact mode, respectively. The H2-TPR and XPS characterization results show that the interaction between Ag and ceria, controlled by precipitant, leads to the high content of the species of Ag+ and Ce3+. It can be concluded that the distribution of silver species with high superficial Ag+/Ag0 ratio and Ag-Ce interface in Ag/CeO2-ZrO2 catalyst does favor the activation and transfer of oxygen species. It appears that the adsorbed oxygen species play an important role in catalytic performance. Moreover, the catalyst/soot contact for the Ag/CeO2-ZrO2 catalyst is expected to be enhanced due to the transfer of oxygen species. The prepared Ag/CeO2-ZrO2 catalyst is repeatedly used five times without any appreciable loss of activity, thus shows good stability initially.

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