Facile fabrication of Au/Fe3O4 nanocomposites as excellent nanocatalyst for ultrafast recyclable reduction of 4-nitropheol

A highly efficient Au/Fe3O4 nanocatalyst is fabricated by using a seed deposition method, and is characterized by XRD, TEM, EDS, XPS, UV-vis and VSM, respectively. TEM image shows that small Au nanoparticles are immobilized onto Fe3O4 surface uniformly and densely. After immersion treatment by NaBH4, the Au/Fe3O4 nanocatalyst exhibits high catalytic efficiency in reducing 4-nitrophenol to 4-aminophenol. The 4-nitrophenol could be fully degraded in less than one minute. The Au/Fe3O4 nanocatalyst demonstrate good magnetic recoverability and high conversion in 1 min (> 98%) after 8 successive cycles. The reaction rate constant k of the catalyst with volume Au sol/mass Fe3O4 microspheres ratio 3 (Au/FeO-3) is 13.8 min(-1), which is 4.7 times larger than that of Au/FeO-1. The catalytic mechanisms were discussed. This work provides a simple and environmentally friendly method for preparing magnetic noble nanocatalyst used for 4-nitrophenol reduction.