Bifunctional Au−Fe₃O₄ Heterostructures for Magnetically Recyclable Catalysis of Nitrophenol Reduction

Abstract

The dumbbell- and flower-like Au−Fe₃O₄ heterostructures by thermal decomposition of the iron−oleate complex in the presence of Au nanoparticles (NPs) have been successfully fabricated using different sizes of Au NPs as the seeds for magnetically recyclable catalysis of <i>p</i>-nitrophenol and 2,4-dinitrophenol reduction. The heterostructures exhibit bifunctional properties with high magnetization and excellent catalytic activity toward nitrophenol reduction. The epitaxial linkages in dumbbell- and flower-like heterostructures are different, leading to the change in magnetic and catalytic properties of the heterostructured nanocatalysts. The pseudo-first-order rate constants for nitrophenol reduction are 0.63−0.72 min⁻¹ and 0.38−0.46 min⁻¹ for dumbbell- and flower-like Au−Fe₃O₄ heterostructures, respectively. In addition, the heterostructured nanocatalysts show good separation ability and reusability which can be repeatedly applied for nearly complete reduction of nitrophenols for at least six successive cycles. The reaction mechanism for nitrophenol reduction by Au−Fe₃O₄ nanocatalysts is also proposed and confirmed by XPS and FTIR analyses. These unique properties make Au−Fe₃O₄ heterostructures an ideal platform to study various heterogeneous catalytic processes which can be potentially applied in a wide variety of fields in purification, catalysis, sensing devices, and green chemistry.