Core-shell structure Ag@Pd nanoparticles supported on layered MnO2 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.