Effect of La Doping on NiCr 2 O 4 Properties and Catalytic Applications toward Decolorization of 4-Nitrophenol

We report the successful synthesis of urea as a fuel for low-temperature microwave combustion-based synthesis of NiCr 2 O 4 and La-doped NiCr 2 O 4 . Synthesis parameters include the kind of precursor, fuel, and container, as well as how external heat is provided to achieve the combustion reaction. Crystal structures, morphology, surface area, solar cells, Fourier-transform infrared spectrometry, and catalytic activity were used to characterize the products. No impurities phase formed in the as-synthesized NiCr 2 O 4 sample, confirmed by XRD. Surface area was measured with a Brunauer–Emmet–Teller adsorption isotherm. Schottky and Frenkel formation energies have been investigated. This demonstrates the time needed for full decolorization of 4-Nitrophenol (yellow color) by NiCr 2 O 4 and La-doped NiCr 2 O 4 . The La-doped NiCr 2 O 4 (0.03%) showed the greatest catalytic activity compared to pristine and other La-doped NiCr 2 O 4 . The decolorization occurs in 10 min. The chemical hardness and surface area of the chromites appear to be important in determining catalytic performance. For multi oxide systems, the counter-doped ions in the A and B sites may alter the metal ion-oxide bond, promoting this partial oxidation process at the interface. The results suggest multiple research subjects focusing on such materials for the future.