Photocatalytic degradation of the AO7 under visible light with Bi-doped SrTiO3

Bismuth doped SrTiO₃ samples, Sr₁-_xBi_xTiO₃ (x=0, 0.05, 0.1 and 0.3), prepared via solid state reaction, were immobilized on Ni-foam and utilized in the photocatalytic degradation of the dye Acid Orange 7 (AO7) under visible light. The Bi-doped samples (x=0.1 and 0.3) presented very good photocatalytic activity - 83 and 77% absorbance removal (484 nm), respectively, after 7-h assays. Since all perovskite samples presented band gap energies pointing to materials with catalytic activity only in the UV (≥3.35 eV), the good photocatalytic activity under visible light can only be explained by the occurrence of a secondary phase for x≥0.1, identified as Bi₄Ti₃O₁₂. Thus, Bi₄Ti₃O₁₂ and mixtures of Bi₄Ti₃O₁₂ with SrTiO₃ and Bi₄Ti₃O₁₂ with Sr_0.95Bi_0.05TiO₃ were prepared and assessed for photocatalytic activity under visible light. Only Bi₄Ti₃O₁₂+Sr_0.95Bi_0.05TiO₃ mixture showed an increase in AO7 absorbance removal of 10% after 7-h assay when compared with the performance of both oxides separately.