Effect of Doping Nickel/Cobalt Ions on Structural, Optical, Morphological and Photocatalytic Efficiency of Zinc Oxide

Zinc oxide (ZnO) has been proven as one of the most researched semiconductors photocatalyst because of its non-toxic nature and physical stability. The efficiency of ZnO as photocatalyst can be improved by doping with transition metals like cobalt (Co) and nickel (Ni). Nevertheless, the interaction between the transition metals with ZnO for photocatalytic studies is still unclear. The present work intrigued to compare the structural, optical, and morphological properties over photocatalytic activity of Co- and Ni-doped ZnO at shorter irradiation time. The results demonstrated that with the addition of Co and Ni dopants, the intensity of the x-ray Diffraction (XRD) patterns decreased suggesting that Co2+ and Ni2+ successfully incorporated to the Zn2+ sites in the crystal. Meanwhile, Fourier Transform Infrared Spectroscopy (FTIR) spectra confirmed the presence of bands assigned to the Zn–O and the absorption peak were quenched with the doping of Ni and Co. The morphological studies using Scanning Electron Microscopy (SEM) shows the heterostructures of ZnO with Co and Ni. The ZnO exhibits irregular nano-grain distribution consisting of tightly packed sphere and ellipsoidal particles while the Co–ZnO and Ni–ZnO samples exhibit quasi-spherical and rod-shaped surface morphologies. The BET isotherms denoted that the samples are classified as type IV which is mesoporous. It is noteworthy that by doping, the energy bandgap decreased from 3.11 eV (ZnO) to 2.98 eV (Co–ZnO) and 3.02 eV (Ni–ZnO). Results revealed that Co-ZnO exhibited better photocatalytic performance within 30 min of irradiation at lower loading of 10 and 30 mg/ml.