The photocatalytic performance and structural characteristics of nickel cobalt ferrite nanocomposites after doping with bismuth

Here, a novel bismuth-doped nickel-cobalt ferrite (Ni_0.5Co_0.5Bi_0.1Fe_1.9O₄) was synthesized using a sol-gel auto-combustion approach. The impact of bismuth substitution on the nickel-cobalt ferrite structural characteristics was investigated relative to the nickel-cobalt ferrite without bismuth substitution (Ni_0.5Co_0.5Fe₂O₄) based on diverse technical options (e.g., scanning electron microscopy-equipped with an energy dispersive X-ray spectrometer, X-ray diffraction, physisorption, and Fourier-transform infrared spectroscopy). Bismuth doping increased the surface area without affecting pore size. The X-ray diffraction pattern confirmed a nano-ferrite cubic spinel structure of the catalyst. Photodegradation of Congo red (CR) was tested using these nickel-cobalt ferrite catalysts under visible light across varying reaction parameters (e.g., pH, catalyst loading, dye concentration, and reaction time). The photo-degradation efficiency for CR in aqueous medium was the highest (98%) at pH 3 with 0.2 g catalyst loading in 100 mL under visible irradiation to reinforce the role of nanostructures as a potent photocatalyst (QY = 2.79 × 10⁻⁷ molecule photon⁻¹). The kinetic reaction rate of Bi-doped spinel ferrite (3.5 µmol g⁻¹ h⁻¹) was1.25 times higher than those undoped materials. This study experimentally proved that the bismuth-doped nickel-cobalt ferrite photocatalyst is an effective option for removing industrial dyes.