NiO and Ag–Cd co-doped NiO nanoparticles: study of photocatalytic degradation of rhodamine B dye for wastewater treatment

For the first time, NiO and Ag–Cd co-doped NiO CdxAg0.30Ni0.70−xO (X = 0.0, 0.05, 0.10, and 0.15) have been synthesized through a facile sol–gel method to investigate the photocatalytic performance by visible-light-driven degradation of rhodamine B dye for wastewater treatment. All samples were characterized through X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray, Fourier transform infrared, photoluminescence, and ultraviolet–visible spectroscopy for structural, morphological, elemental, functional groups, optical, and bandgap analysis, respectively. Face-centered cubic structure of NiO was confirmed through X-ray diffraction. The formation of NiO and Ag–Cd co-doped NiO nanoparticles was confirmed through elemental and functional groups analysis. Optical properties obtained from photoluminescence spectroscopy revealed visible-light emission spectrum and slower electron/hole pair recombination rate with an increase in doping. Minimum optical bandgap energy of 2.37 eV was found for the Cd0.15Ag0.30Ni0.55O sample. Photocatalytic performance study revealed that degradation followed first-order kinetics. Cd0.15Ag0.30Ni0.55O was the best sample which showed the maximum efficiency of 97%, the reaction rate constant K (min−1) of 0.0496, and the correlation coefficient (R2) of 0.988 after 140-min degradation of rhodamine B dye. The reusability and stability of the best sample were checked for six cycles by obtaining an X-ray diffraction pattern after the photocatalytic process.