Combustion synthesis and analysis of visible-light-driven Ho-doped ZnO photocatalytic nanoparticles

ZnO nanoparticles with different Ho dopant were prepared by tartaric acid solution combustion method and followed by calcination at 600°C for 2 h.The XRD patterns of ZnO and Ho-doped ZnO samples were indexed to the pure phase of hexagonal wurtzite ZnO structure.TEM images of ZnO and Ho-doped ZnO showed that the samples were nanoparticles with different sizes.The particle size of sample was decreased with increasing in the weight content of Ho dopant.The XPS results certified that the Ho 3+ ions contained in ZnO lattice.The photocatalytic activity of the as-synthesized ZnO nanoparticles with different Ho contents was evaluated through the degradation of methylene blue (MB) as a dye pollutant under visible light irradiation.The photodegradation of MB in aqueous medium under visible light irradiation showed that the 3% Ho-doped ZnO nanoparticles have the highest photocatalytic activity in degrading of MB molecules because Ho 3+ ions played the role in trapping electrons, inhibiting the recombination charge carrier pairs and enhancing the photocatalytic performance of ZnO under visible light irradiation.