Photocatalytic efficiencies of Ni, Mn, Fe and Ag doped ZnO nanostructures synthesized by hydrothermal method: The synergistic/antagonistic effect between ZnO and metals

The ZnO and different noble and transition metals (Ni, Mn, Fe and Ag) doped ZnO (M/ZnO) nanostructures were synthesized by hydrothermal method. The ZnO and M/ZnO photocatalysts were characterized by Xray diffraction (XRD), field emission scanning electron microscopy (FESEM), fourier transform infrared (FTIR) and UV-vis spectrophotometry. The obtained XRD and FESEM results confirmed the well dispersion of Ni and Ag nanoparticles and highly agglomerated Mn and Fe nanoparticles on the surface of ZnO nanostructures. The optical band gap value was calculated as 3.24, 3.15, 3.10, 3.05 and 3.00 eV from UV-vis diffuse reflectance spectra of ZnO, Ag/ZnO, Ni/ZnO, Fe/ZnO and Mn/ZnO photocatalysts, respectively. The results of the photocatalytic degradation of tartrazine in aqueous solutions under the UV-light showed that Ni/ZnO exhibited higher photocatalytic activity than the other ones. Mn/ZnO demonstrated the lowest photocatalytic activity among the synthesized photocatalysts. Thus, Ni and Ag exhibited synergistic effect while Fe and Mn exhibited antagonistic effect on the ZnO photocatalytic activity. The maximum degradation rate of tartrazine was obtained to be 98.2% in the 60 min using Ni/ZnO. The plausible mechanisms were proposed and discussed for the enhanced or decreased photocatalytic activities resulting from different metals doped ZnO. (C) 2017 Elsevier B.V. All rights reserved.