Effect of calcination temperature on the structure and hydroxylation activity of Ni0.5Cu0.5Fe2O4 nanoparticles

Nanocrystalline Ni0.5Cu0.5Fe2O4 was synthesized by sol-gel method with varying calcination temperature over the range of 500-1000. The powders obtained were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). In addition, thermal analysis (TG-DTG-DTA) of the precursor was carried out. The study reveals the simultaneous decomposition and ferritization process at rather low temperature (280-350). For the crystalline structure investigated, single cubic spinel is gained when the precursor was decomposed at 800-1000, whereas separated crystal CuO formed when calcination temperature is below 800. The increase of calcination temperature favors the appearance of FeB3+, CuA2+ and O on the spinel surface. The hydroxylation activity is relative to the amount of CuB2+ species on the spinel surface. The lattice oxygen species on the spinel surface are favorable for the deep oxidation of phenol.

Research highlights► The decomposition and ferritization occur simultaneously at 280-350 °C. ► 800 °C is required for the formation of homogeneous cubic spinel. ► High calcination temperature makes more FeB3+, CuA2+ and OI on the surface. ► CuB2+ species on the spinel surface is active for the hydroxylation.