Enhanced photo-decomposition of methylene blue and toluene with (Ag,Na)-TiO2/Sr4All4O25:Eu,Dy heterojunction photocatalyst synthesized by coprecipitation method

Abstract

The TiO₂/Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ heterojunction photocatalyst has been prepared by TiO₂ nanoparticles coated on the Sr₄Al₁₄O₂₅:Eu,Dy phosphor substrate using a coprecipitation reaction method. To improve the generation of charge carriers in the photocatalyst, Na and Ag elements were impregnated on TiO₂ nanoparticles by adding NaHCO₃ and AgNO₃, respectively. The (Ag,Na)-impregnated TiO₂/Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ hybrid photocatalyst system was synthesized under various conditions, including different Ag concentrations (0–0.08 M) and heat treatment temperatures (200–500 °C). The photocatalytic performance of (Ag,Na)-impregnated TiO₂/Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ hybrid photocatalysts was analyzed through the photobleaching of methylene blue(MB) dye solution and decomposition of toluene gas. In the hybrid photocatalysts of TiO₂-coated long-lasting phosphors, the phosphor may act as an internal light source toward the acceleration or sustenance of photocatalytic reactivity even in the absence of external light irradiation. The photocatalytic reactivity of (Ag,Na)-TiO₂/Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ hybrid photocatalyst surpassed that of Na-TiO₂/Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ without Ag impregnation. The (0.06 M Ag, Na)-TiO₂/Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ photocatalyst and TiO₂/Sr₄Al₁₄O₂₅: Eu²⁺,Dy³⁺ without Ag impregnation degraded a 10 ppm toluene gas about 65% and 30% in 150 min under visible light, respectively. This superior performance can be primarily ascribed to the synergistic interaction between (Ag,Na) and TiO₂.