Enhanced photocatalytic reaction of (TiO₂–WO₃) on Sr₄Al₁₄O₂₅:Eu,Dy long-lasting phosphor

(TiO₂–WO₃)/Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ heterojunction photocatalysts were prepared by coating (TiO₂–WO₃) nanoparticles onto a Sr₄Al₁₄O₂₅ phosphor substrate using a hydrothermal synthesis. The photocatalytic properties were investigated with respect to various ratios of TiO₂ to WO₃ (10:0, 7:3, 5:5, 3:7, 0:10) and heat treatment temperatures ranging from 300 to 700 °C. The combination of TiO₂ and WO₃ enhanced photocatalytic efficiency by leveraging the high photocatalytic oxidation capability of TiO₂ and the broad visible light absorption range of WO₃. The photocatalytic response was analyzed through the photobleaching of methylene blue (MB) dye and the decomposition of toluene gas. In the hybrid photocatalyst of (TiO₂–WO₃) coated on Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ long-lasting phosphor, the phosphor might act as an internal light source to accelerate or sustain photocatalytic reactivity, even in the absence of external light irradiation. The heterojunction of (TiO₂–WO₃) and Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ reduced the energy band gap and enhanced visible light absorption, thereby improving photocatalytic reactivity. The 5:5 ratio of TiO₂ to WO₃ on Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ showed excellent photocatalytic performance, decomposing over 80% degradation of methylene blue dye within 90 min and 67% of toluene gas within 90 min under visible-light irradiation. In particular, the persistent luminescence of Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ enabled continuous photocatalytic activity even under dark condition, achieving ~ 67% decomposition of toluene gas after 180 min without light irradiation. The photocatalytic reactivity of (TiO₂–WO₃)/Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ surpassed those of TiO₂/Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ and WO₃/Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺, primarily due to the synergistic interaction between TiO₂ and WO₃.