Effect of preparation method on the surface properties and activity of Ni0.7Cu0.3Fe2O4 nanoparticles

Ni0.7Cu0.3Fe2O4 nanoparticles were synthesized via sol–gel combustion technique, co-precipitation method and solid state milling method. Simultaneous thermogravimetric and differential thermal analysis (TG–DTA) was carried out to monitor the decomposition process of the precursors. The samples were characterized by Fourier transform infrared (FT-IR), inductively coupled plasma spectroscopy (ICPS), X-ray diffraction (XRD), BET surface area measurement, scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). TG–DTA traces of the precursors show that the crystallization temperature for spinel formation by sol–gel combustion technique is lower than those by co-precipitation method and solid state milling method. XRD analysis reveals that the powders obtained are single phase with cubic spinel structure. Mutual promotion of reduction performance between CuO and NiFe2O4 is observed from TPR patterns. The experimental study indicates that the copper in the octahedral sites plays a crucial role in the direct oxidation of benzene with hydrogen peroxide as oxidant to phenol.