Photocatalytic reaction of composite of TiO₂ hydrothermally coated on (Cu-doped Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺) phosphor

Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ phosphor powder support for TiO₂ catalyst was synthesized by a solution combustion method and thermally treated in N₂-H₂ reducing atmosphere. To investigate the effect of Cu transition metal ion on phosphor, varying amounts of copper (II) nitrate trihydrate solution were impregnated on Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ powder. TiO₂-sol was hydrothermally coated on the Cu-doped Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ phosphor powder at 2-, 4-, 6-, and 8-h reaction times. The major X-ray diffraction peaks of the as-synthesized Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ phosphor support were preserved even after Cu doping and TiO₂ hydrothermal coating. Scanning electron microscopy (SEM) images revealed the growth of interconnected nano flakes with Cu addition, which were destroyed by longer reaction times. Methylene blue solution and toluene vapor were used for testing the photocatalytic properties of the TiO₂ hydrothermally coated Cu-doped Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ phosphor composites. The most outstanding photocatalytic reactions under both ultraviolet and visible light were exhibited by 0.062 M Cu phosphor coated with TiO₂ for 4 h by hydrothermal reaction. This superior photocatalytic reaction was attributed to a dense nano flake morphology with higher specific surface area compared with 8-h hydrothermally and sol–gel coated samples. Thus, more active sites and a lower energy band imparted by Cu doping improved the light sensitization and electron–hole separation efficiencies.