Role of Mn2+ Doping on Structural, Morphological, and Opto-Magnetic Properties of Spinel Mn x Co1-x Fe2O4 (x=0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) Nanocatalysts

Spinel MnxCo(1-x) Fe2O4; x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) nanoparticles were synthesized by ureaassisted auto combustion method using nitrates of Co, Mn and Fe as the starting materials and urea as the fuel. X-ray diffraction (XRD) analysis showed that all composition was found to have a cubic spinel structure. The average crystallite size of the samples was estimated using the Debye-Scherrer formula and was found to be in the range of 22.62 and 36.45 nm. The lattice parameter increased from 8.432 to 8.457 with increasing the Mn2+ content, which was determined by Rietveld analysis. High-resolution scanning electron microscopy (HR-SEM) and high-resolution transmission electron microscopy (HR-TEM) analyses were used to study the morphological variation, and the results showed a nanosized particle-like morphology. Energy-dispersive X-ray (EDX) results showed that the composition of the elements was relevant as expected from the synthesis. The bandgap energy of the pure CoFe2 O (4) was estimated to be 2.33 eV from UV-visible diffuse reflectance spectroscopy (DRS). With the increase of Mn2+ ion, the bandgap energy increased from 2.35 to 2.42 eV. The magnetic properties of the samples were investigated at room temperature by using a vibrating sample magnetometer (VSM). The magnetic hysteresis (M-H) loop confirmed the superparamagnetic nature of pure CoFe2 O (4) and a weak ferromagnetic behavior of Mn(2+)doped CoFe2 O (4) samples with specific saturation magnetization in the range of 55.16 +/- 24 and 66.92 +/- 05 emu/g. All compositions of spinel Mn (x) Co1-x Fe-2 O (4) samples were successfully tested as catalyst for the conversion of benzyl alcohol, which has resulted in 62.75 and 92.62 % conversion efficiency of CoFe2 O (4) and Mn0.5Co0.5Fe2 O (4), respectively.