A simple way to prepare Au@polypyrrole/Fe3O4 hollow capsules with high stability and their application in catalytic reduction of methylene blue dye

Abstract

Metal nanoparticles are promising catalysts for dye degradation in treating wastewater despite the challenges of recycling and stability. In this study, we have introduced a simple way to prepare Au@polypyrrole (PPy)/Fe₃O₄ catalysts with Au nanoparticles embedded in a PPy/Fe₃O₄ capsule shell. The PPy/Fe₃O₄ capsule shell used as a support was constructed in one-step, which not only dramatically simplified the preparation process, but also easily controlled the magnetic properties of the catalysts through adjusting the dosage of FeCl₂·4H₂O. The component Au nanoparticles could catalyze the reduction of methylene blue dye with NaBH₄ as a reducing agent and the reaction rate constant was calculated through the pseudo-first-order reaction equation. The Fe₃O₄ nanoparticles permitted quick recycling of the catalysts with a magnet due to their room-temperature superparamagnetic properties; therefore, the catalysts exhibited good reusability. In addition to catalytic activity and reusability, stability is also an important property for catalysts. Because both Au and Fe₃O₄ nanoparticles were wrapped in the PPy shell, compared with precursor polystyrene/Au composites and bare Fe₃O₄ nanoparticles, the stability of Au@PPy/Fe₃O₄ hollow capsules was greatly enhanced. Since the current method is simple and flexible to create recyclable catalysts with high stability, it would promote the practicability of metal nanoparticle catalysts in industrial polluted water treatment.