Role of Different Fuels and Sintering Temperatures in the Structural, Optical, Magnetic, and Photocatalytic Properties of Chromium-Containing Nickel Ferrite: Kinetic Study of Photocatalytic Degradation of Rhodamine B Dye.

In the present paper, nanocrystalline samples of NiCrFeO were synthesized by the combustion method using different fuels such as glycine, urea, and poly(vinyl alcohol) and subjected to heat treatment at different temperatures of 600, 700, 800, and 1000 °C for 6 h. The formation of phases with highly crystalline structures was confirmed by XRD and Rietveld refinement analysis. The optical band gap of NiCrFeO ferrites lies in the visible range, making them suitable photocatalysts. BET analysis reveals that the surface area of the phase synthesized using PVA is much higher than that synthesized using other fuels at each sintering temperature. In addition, there is a significant decrease in the surface area with sintering temperature for the catalysts prepared using the fuels PVA and urea, while it almost remains constant in the case of glycine. Magnetic studies demonstrate the dependence of saturation magnetization on the nature of the fuel and on the sintering temperature; moreover, the coercivity and squareness ratio confirm the single domain nature of all the synthesized phases. We have also performed photocatalytic degradation of the highly toxic Rhodamine B (RhB) dye by employing all the prepared phases as photocatalysts using the mild oxidant HO. It is observed that the photocatalyst prepared using PVA as the fuel exhibited the best photocatalytic activity at all sintering temperatures. All the three photocatalysts prepared using different fuels showed a decrease in the photocatalytic activity with increasing sintering temperature. From the chemical kinetic point of view, the degradation of RhB by all the photocatalysts was found to follow pseudo-first-order kinetics.