Catalysts of self-assembled Pt@CeO2-delta-rich core-shell nanoparticles on 3D ordered macroporous Ce1-xZrxO2 for soot oxidation: nanostructure-dependent catalytic activity

摘要

The catalytic performance in heterogeneous catalytic reactions consisting of solid reactants is strongly dependent on the nanostructure of the catalysts. Metal-oxides core-shell (MOCS) nanostructures have potential to enhance the catalytic activity for soot oxidation reactions as a result of optimizing the density of active sites located at the metal-oxide interface. Here, we report a facile strategy for fabricating nanocatalysts with self-assembled Pt@CeO2-delta-rich core-shell nanoparticles (NPs) supported on three-dimensionally ordered macroporous (3DOM) Ce1-xZrxO2 via the in situ colloidal crystal template (CCT) method. The nanostructure-dependent activity of the catalysts for soot oxidation were investigated by means of SEM, TEM, H-2-TPR, XPS, O-2-isothermal chemisorption, soot-TPO and so on. A CeO2-delta-rich shell on a Pt core is preferentially separated from Ce1-xZrxO2 precursors and could self-assemble to form MOCS nanostructures. 3DOM structures can enhance the contact efficiency between catalysts and solid reactants (soot). Pt@CeO2-delta-rich core-shell nanostructures can optimize the density of oxygen vacancies (O-v) as active sites located at the interface of Pt-Ce1-xZrxO2. Remarkably, 3DOM Pt@CeO2-delta-rich/Ce1-xZrxO2 catalysts show super catalytic performance and strongly nanostructure-dependent activity for soot oxidation in the absence of NO and NO2. For example, the T-50 of the 3DOM Pt@CeO2-delta-rich/Ce0.8Zr0.2O2 catalyst is lowered down to 408 degrees C, and the reaction rate of the 3DOM Pt@CeO2-delta-rich/Ce0.2Zr0.8O2 catalyst (0.12 mu mol g(-1) s(-1)) at 300 degrees C is 4 times that of the 3DOM Pt/Ce0.2Zr0.8O2 catalyst (0.03 mu mol g(-1) s(-1)). The structures of 3DOM Ce1-xZrxO2-supported Pt@CeO2-delta-rich core-shell NPs are decent systems for deep oxidation of solid reactants or macromolecules, and this facile technique for synthesizing catalysts has potential to be applied to other element compositions.