Investigation of cation (Sn 2+) and anion (N 3−) substitution in favor of visible light photocatalytic activity in the layered perovskite K 2La 2Ti 3O 10

Abstract

Noticeable lowering of the energy gaps have been achieved for the layered perovskite K 2La 2Ti 3O 10 as a result of the attempts made to incorporate Sn 2+ and N 3− ions. Incorporation of Sn 2+ ions was carried out by the ion-exchange reaction of K 2La 2Ti 3O 10 with aqueous tin(II) chloride solution. Nitrogen incorporation was attempted by the solid state reaction of the parent oxide with urea around 400 °C in air. The resultant oxides have been characterized by power X-ray diffraction, UV–visible diffuse reflectance spectroscopy, and Fourier transform infrared spectroscopy. Room temperature ion-exchange was sufficient to introduce Sn 2+ ions with the resulting product of composition (Sn 0.45K 0.2H 0.9)La 2Ti 3O 10·H 2O. Visible light absorption was observed with the absorption edge red shift of ∼100 nm from that of the parent K 2La 2Ti 3O 10. The lowering of the band gap was as expected by the contribution of Sn 5s orbitals to the O 2p orbitals in the formation of the valence band. Nitridation using urea resulted not only in nitrogen doping but with the additional sensitization by the presence of carbon nitride (CN) polymers, which again resulted in visible light absorption. The product oxides obtained as a result of cation and anion intended substitutional studies have been found to be useful for the visible light photocatalytic decomposition of organic dyes such as rhodamine B.