Fabrication of Bi-Fe₃O₄@RGO hybrids and their catalytic performance for the reduction of 4-nitrophenol

Nanocatalysts are frequently connected to magnetic nanoparticles. These composites are easy to be retrieved from the reaction system under a magnetic field because of their magnetic properties. Magnetic separation is particularly promising in industry since it can solve many issues present in filtration, centrifugation, or gravitation separation. Herein, a facile method to prepare bismuth and Fe₃O₄ nanoparticles loaded on reduced graphene oxide magnetic hybrids (Bi-Fe₃O₄@RGO) using soluble starch as a dispersant is demonstrated. The magnetic Fe₃O₄ nanoparticles were synthesized by the co-precipitation of Fe²⁺ and Fe³⁺ ions, and Bi nanoparticles were fabricated by the redox reactions between sodium borohydride and ammonium bismuth citrate in the presence of soluble starch. Transmission electron microscopy images demonstrate that the average diameter of the Fe₃O₄ nanoparticles is about 5 nm and the diameters of Bi nanoparticles range from 10 to 20 nm. The magnetic Bi-Fe₃O₄@RGO hybrids exhibit high catalytic activity in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH₄ with a first-order rate constant (K) of 0.00808 s⁻¹ and is magnetically recyclable for at least five cycles. This strategy provides an efficient and recyclable catalyst for the use in environmental protection applications