Phyto‐fabricated MgNiO 2 ternary metal oxides for enhanced photocatalytic degradation of organic pollutants

Nickel oxide nanoparticles (NiO NPs), Magnesium oxide nanoparticles (MgO NPs), and MgNiO 2 ternary metal oxide nanoparticles (MN NPs) were prepared using a green method that employed Sonneratia ovata leaf extract. X‐ray diffraction (XRD) results validated the cubic structure, revealing typical crystallite sizes of 10.01 nm for NiO, 22.67 nm for MgO, and 14.82 nm for MN NPs. Fourier transform infrared (FTIR) spectra identified functional groups in both metal oxides and phytochemicals, whereas the optical results indicated absorption edges at 307 nm (NiO), 214 nm (MgO), and 288 nm (MN NPs). Morphological and particle‐size analyses revealed uniformly distributed nanostructures with average particle sizes of 20.73, 38.55, and 25.38 nm. The elemental mapping confirmed the uniform incorporation of Ni, Mg, and O, whereas X‐ray photoelectron spectra (XPS) revealed the oxidation states Ni 2+ and Mg 2+ on oxygen‐rich surfaces. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) revealed improved charge transfer, reduced resistance, and enhanced redox reversibility in MN NPs compared with the individual oxides. Photocatalytic analyses conducted under sunlight using a dye concentration of 10 mg/L and a catalyst dosage of 1 g/L revealed that MN NPs exhibited the highest degradation efficiencies for Congo red (98.95%), Crystal violet (95.26%), and paracetamol (99.07%), following pseudo‐first‐order kinetics, while recycling tests demonstrated significant stability (>92% efficiency after five cycles). The findings indicate that the synergistic structural formation between NiO and MgO enhances charge separation, radical generation, and pollutant mineralization, highlighting MN NPs as a cost‐effective and environmentally benign nanocatalyst for wastewater treatment and multifunctional applications.