Visible-light driven catalytic activity of two novel Cu(II) and Ni(II) titanium niobates

Abstract Novel copper (Cu 0.25 Ti 0.25 Nb 0.5 O 2 ) and nickel (Ni 0.25 Ti 0.25 Nb 0.5 O 2 ) titanium-niobate materials were synthesized by the solid state method and fully characterized. In view of their band gap energies in the visible region, these materials were tested as catalysts to degrade Indigo Carmine, chosen as a prototype organic molecule. Aqueous solutions of this dye with hydrogen peroxide and the above-mentioned materials were irradiated with visible light. Hydrogen peroxide was employed aiming at reducing the recombination rate of the photogenerated charges and to increase the production of hydroxyl radicals. In these experimental conditions, the Cu(II)-based material (Cu-Nb) showed a superior performance than the Ni(II) analogue (90% versus 20% degradation efficiency after an exposure time of 150 min, respectively). The results seem to indicate that the degradation probably takes place via two distinct heterogeneous processes: photocatalysis and photo-Fenton-like. Finally, the Cu-Nb material has a remarkable potential to be used in the remediation of water bodies contaminated with organic pollutants.