Plant-mediated biosynthesis of Nickel (II) oxide nanoparticles from Calpurnia Aurea Leaf extract: A promising photocatalyst for malachite green degradation

The current work investigation involves the synthesis of NiO NPs using Calpurnia Aurea leaf aqueous extract-based phytocompounds as NPs facilitating agents for application as effective photocatalyst in the degradation of MG. The obtained NiO NPs were characterized using various techniques, including FTIR, XRD, and SEM. The XRD analyses of NiO NPs indicated the crystalline nature of NiO NPs showed that face- center cubic structure with the average crystalline size, the specific surface area, and percent of crystallinity are 17.61 nm, 49.5 m 2 /g, and 91.4% respectively. FTIR analysis showed the presence of a stretching frequency peak at 438 and 557cm -1 , confirming the Ni–O band stretching. Results demonstrated that NiO NPs showed high photo-catalytic rates with 98.17% degradation of Malachite green (MG) within 30 min under visible light irradiation. Moreover, NiO NPs calcined at 400°C was more efficient photo-catalyst than the other NiO NPs calcined at 300°c, and 500°C with 1.41, and 2.96 times higher kinetic rates for the removal of MG, respectively. The active species involved in degradation process were systematically investigated and a photo-catalytic mechanism was proposed. In addition, NiO NPs showed good recyclability and reusability of resistance to photo-corrosion even after 120 minutes of consecutive photo-catalytic activity. Overall, the green synthesized NiO NPs exhibited considerable potential for fast and eco-friendly removal of harmful organic dyes.