Ni@Pd core–shell nanoparticles immobilized on yolk–shell Fe3O4@polyaniline composites as a highly efficient, magnetically separable and atom‐economical catalyst for reduction of nitrobenzenes

Abstract

The preparation of Ni@Pd core–shell nanoparticles immobilized on yolk–shell Fe3O4@polyaniline composites is reported. Fe3O4 nanoclusters were first synthesized through the solvothermal method and then the SiO2 shell was coated on the Fe3O4 surface via a sol–gel process. To prepare Fe3O4@SiO2@polyaniline composites, polyvinylpyrrolidone was first grafted on to the surface of Fe3O4@SiO2 composites and subsequently polymerization of aniline was carried out via an ultrasound‐assisted in situ surface polymerization method. Selective etching of the middle SiO2 layer was then accomplished to obtain the yolk–shell Fe3O4@polyaniline composites. The approach uses polyaniline (PANI) conductive polymer as a template for the synthesis of Ni@Pd core–shell nanoparticles. The catalytic activity of the synthesized yolk–shell Fe3O4@PANI/Ni@Pd composite was investigated in the reduction of o‐nitroaniline to benzenediamine by NaBH4, which exhibited conversion of 99% in 3 min with a very low content of the catalyst. Transmission electron microscopy, X‐ray photoelectron spectroscopy, TGA, X‐ray diffraction, UV–visible, scanning electron microscopy, X‐ray energy dispersion spectroscopy and FT‐IR were employed to characterize the synthesized nanocatalyst. Copyright © 2014 John Wiley & Sons, Ltd.