Fabrication of reduced graphene oxide decorated with gold and nickel for the catalytic reduction of 4-nitrophenol

Reduced graphene oxide (Ni/rGO) decorated by metallic Ni nanoparticles (NPs) was firstly fabricated through in situ thermal decomposition and subsequent reduction in 5% H₂/N₂ gas at 600 °C, and then Au NPs were loaded on the surface of the as-prepared Ni/rGO. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM) were used to characterize the Ni-decorated rGO and Ni/rGO@Au nanocomposites. The results show that both Ni and Au NPs are highly dispersed on rGO, and Ni/rGO@Au possesses excellent activity toward the conversion of 4-nitrophenol into 4-aminophenol in the presence of NaBH₄, showing almost four orders of magnitude higher activity parameter κ (9.7 × 10⁻² s⁻¹mg⁻¹) than Ni/rGO (1.1 × 10⁻⁵ s⁻¹mg⁻¹), though Ni/rGO has a better performance in the catalytic conversion of 4-NP. In the meantime, the Ni/rGO@Au can be easily recycled by an external magnetic field and the conversion of 4-nitrophenol at the 8th cycle is still close to 95%.