Core-shell structure Ag@Pd nanoparticles supported on layered MnO 2 substrate as toluene oxidation catalyst

Abstract

The silver palladium bimetallic core-shell structure nanoparticles (Ag@Pd NPs) were synthesized by a thin Pd shell slowly generating on the outmost of Ag nanoparticle according to galvanic replacement mechanism. Then, the 2D layered structure manganese dioxide (MnO₂) substrate was used to support the as-synthesize Ag@Pd NPs to prepare Ag@Pd/MnO₂ catalyst for toluene purification in oxidation reaction. Physicochemical properties of the samples were characterized by a number of different analytical techniques. It is found that the Ag@Pd NPs are homogeneously spherical shape with an average particle diameter size of 7.1 nm. And the MnO₂ substrate can not only uniformly disperse Ag@Pd active component on its surface for its high specific surface area and mesopore volume, but also provide the reactive lattice oxygen by its mixed oxidation states of Mn³⁺/Mn⁴⁺. Moreover, the core-shell configuration of Ag@Pd NPs can improve the state phase transformation from Pd⁰ to PdO₂ with the aid of lattice oxygen of MnO₂ substrate, because of the lattice oxygen migration controlled strong metal-support interaction (SMSI) effect between palladium active component and MnO₂ substrate. So, there would be more exposed PdO₂ active sites on the Ag@Pd/MnO₂ catalyst relative to monometallic Pd/MnO₂ catalyst. Hence, the as-prepared bimetallic core-shell Ag@Pd/MnO₂ catalyst exhibits greatly higher toluene oxidation activity at lower reaction temperature than monometallic Pd/MnO₂ catalyst, indicating it is a promising catalyst for use in volatile organic compounds (VOCs) purification.

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