摘要： In this study, Ni0.5-xCoxCu0.5Fe2O4 (with x varying from 0.0 to 0.5) ferrites have been synthesized by a sol-gel auto-combustion method using urea as fuel. The influence of Cobalt (Co2+) content on the structural, optical and magnetic Ni-Cu ferrites was studied by X-ray diffraction (XRD) patterns, Fourier Transform Infrared Spectroscopy (FT-IR), UV-Vis Spectroscopy (UV-DRS) and vibrating sample magnetometer (VSM). Scanning electron microscopy (SEM) and Energy dispersive X-ray (EDX) analysis have been used to determine morphology and compositions respectively. The X-ray diffraction studies have been carried out by considering the distance between adjacent crystal planes, lattice constant and average crystallite size which decrease from 44-35 nm with substitution of Co2+. FT-IR spectra show two major stretching bands around 400-600 cm-1. The magnetic parameters were measured at room temperature where increase in saturation magnetization was observed with increase in concentration of Co2+ in Ni-Cu ferrites. The photocatalytic performance study of Co2+ substituted Ni-Cu ferrites was carried out under visible and direct sunlight on methylene blue (MB) dye. The increase in degradation percentage was observed with Co2+ substitution in both visible and sunlight. The catalyst was found to be more efficient in sunlight with 91% degradation of MB within 120 minutes.