Magneto-Optical and Catalytic Properties of Recyclable Spinel NiAl 2 O 4 Nanostructures Using Facile Combustion Methods

Abstract

Spinel nickel aluminate (NiAl 2 O 4) nanospheres (NSPs) and nanoplatelets (NPLs) were successfully synthesized using a facile microwave combustion method (MCM) and conventional combustion method (CCM), respectively, using urea as the fuel. The as-prepared samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), high-resolution scanning electron microscopy (HR-SEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED), UV–Visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, and vibrating sample magnetometer (VSM) analysis. Powder XRD, FT-IR, EDX, and SAED results showed that the samples were pure phase spinel NiAl 2 O 4 nanocrystals without any other secondary phase impurity. UV–Vis DRS and PL spectroscopy results were used to calculate the energy band gap (E g) value of the samples which is 3.41 and 3.08 eV for NiAl 2 O 4 NSPs and NiAl 2 O 4 NPLs, respectively. VSM results of the NiAl 2 O 4 NPLs sample show lower M s (49.16 × 10 −3 emu/g) values compared with the NiAl 2 O 4 NSPs sample (73.42 × 10 −3 emu/g), which confirm that both the products have ferromagnetic behavior. NiAl 2 O 4 NSPs were found to have higher surface area than NiAl 2 O 4 NPLs, which in turn leads to the improved performance towards the selective oxidation of benzyl alcohol into benzaldehyde, with 100 % selectivity, and it was found that the NiAl 2 O 4 NSPs sample show higher conversion (96.25 %) than NiAl 2 O 4 NPLs (85.37 %). The as-prepared samples show high activity, good reusability, remarkable stability, and environmentally friendly materials for industrial and technological applications.