Structural, magnetic and catalytic properties of cobalt chromite obtained through precursor method

Cobalt chromite (CoCr2O4) was synthesized through the precursor method. The precursors: (NH4)3[CoCr2(C4O6H4)4(OH)3]·4H2O, (NH4)3[CoCr2(C6O7H10)4(C6O7H9)]·5H2O were characterized by elemental chemical analysis, infrared (IR) and ultraviolet–visible (UV–vis) spectroscopy, and thermal analysis. The final oxides were characterized by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM), UV–vis, IR, Raman spectroscopy (RS), magnetic measurements, N2 adsorption–desorption analyses and X-ray photoelectron spectroscopy (XPS). XRD confirmed the cubic CoCr2O4 phase only and determined average crystallite sizes between 14 and 21 nm. Electron microscopy revealed morphology corresponding to the complete crystallization into cubic CoCr2O4. All the samples presented ferrimagnetic ordering below the Currie temperature (Tc), and a phase transition at Ts ∼26 K attributed to the onset of long-range spiral magnetic order. The CoCr2O4 nanoparticles generated through the gluconate route following calcination at 700 °C for 1 h were found to have the best catalytic activity in the total oxidation of methane.