Photocatalytic Composite Sr2MgSi2O7:(Eu, Dy)/g-C3N4: A Z-Scheme Heterojunction Material Formed by Long-Afterglow Phosphors and Photocatalysts on Round-the-Clock Photocatalytic Degradation of Methylene Blue

The long-afterglow luminescent material Sr2MgSi2O7:(Eu, Dy) was combined with the photocatalytic material g-C3N4 to construct a type of Sr2MgSi2O7:(Eu, Dy)/g-C3N4 self-luminous photocatalytic composite. This overcomes the limitation that photocatalytic experiments can only be carried out under an external light source, and it provides a more flexible way to use photocatalytic technology in environmental purification. The morphology, structure, luminescence, and photocatalytic properties of the samples were investigated using a variety of advanced characterization techniques. The results show that the significant improvement in the photocatalytic performance is attributed to the formation of a Z-scheme heterojunction between the luminescent and photocatalytic materials and the promotion of the photocatalytic reaction by the properties of the long-afterglow luminescent material itself. A possible mechanism for the photocatalytic process of the composite is proposed, and it is speculated that the reason for the increased photocatalytic activity is internal electron transfer and electron-hole pair separation based on tests such as X-ray photoelectron spectroscopy and density functional theory calculations. This study provides a strategy for enhancing the photocatalytic activity of photocatalysts and achieving round-the-clock degradation of pollutants.