Solvothermal synthesis of octahedral NiFe2O4 nanocrystals and catalytic properties for the reduction of some aromatic nitrocompounds

In this paper, we report the successful synthesis of octahedral NiFe2O4 nanocrystals with room-temperature ferrimagnetism via a mixed solvothermal process at 170 °C for 15 h, using Fe(NO3)3 and NiCl2 as starting reactants. The phase and morphology of the as-prepared product is characterized by means of powder X-ray diffraction, energy dispersive spectrometry, selected area electron diffraction (SAED), (high resolution) transmission electron microscopy, and scanning electron microscopy. Experiments showed that the as-prepared octahedral NiFe2O4 nanocrystals owned strong catalytic activity for the reduction of some aromatic nitro-compounds such as 4-nitrophenol, 2-nitroaniline, 4-nitroaniline, and 2,4-dinitrophenol. Under the presence of 9 mg NiFe2O4 nanocrystals, the rate constants of the reductive reactions were in turn 3.16 × 10−2 min−1 for 4-nitrophenol, 4.28 × 10−2 min−1 for 2-nitroaniline, 6.79 × 10−2 min−1 for 4-nitroaniline, and 3.26 × 10−2 min−1 for 2,4-dinitrophenol. Moreover, the present catalyst could be conveniently recycled due to its magnetism. After ten cycles, its catalytic efficiency did not obviously decrease.