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.