The precursor nanoparticles of nickel hydroxide (Ni(OH)2) and nickel oxide (NiO) were successfully converted into the latter by the reaction of nickel chloride with hydrazine at ambient temperature. (TGA) and (DSC) were adapted for annealing the precursor products at different annealing temperatures (210, 285, 350, 390, 425, and 450 °C). XRD, TEM, and UV-VIS absorption spectroscopy were used to characterize the products. Both the band edge and energy gap values decrease with increasing annealing temperatures. Hysteresis loops are visible in the M-H curves of annealed (350 °C and 390 °C) precursor NiO NPs, indicating the presence of ferromagnetic Ni domains. However, NiO nanoparticles annealed at higher temperatures (425 °C and 450 °C) had a straight M-H curve, indicating paramagnetic properties. NiO NPs were used to study photocatalysis in the degradation of the MB dye. As annealing temperatures increased, the catalyst caused the degradation of MB. The sample that was annealed at 450 °C, however, exhibits the maximum photocatalytic activity, reaching up to 72.4% after being exposed to visible light. In other words, it was discovered that as the catalyst's annealing temperature rose, so did the rate of MB's photocatalytic degradation.
Keywords: nickel oxide nanoparticles; optical properties; photocatalyst; structural analysis; thermogravimetric analysis.