Continuous photocatalysis is achieved by using light-storing assisted photocatalytic composites, but little is known about the interactions between photocatalysts and long afterglow materials. g-C 3 N 4 /Sr 2 MgSi 2 O 7 :(Eu,Dy) with a sustained reaction activity was prepared by pyrolysis polymerization, and its optical-photocatalysis behaviors were studied. It was found that the light absorption ability and NO removal effect were improved, but the luminescence-afterglow performance became worse. The interface model of g-C 3 N 4 /Sr 2 MgSi 2 O 7 :(Eu,Dy) was constructed for the first time. On the basis of experimental analyses, its electronic structure and carrier transfer paths were studied by First-principles calculations, and reasons behind the changes in macro performance were revealed. The results showed that Eu 4 f electrons are difficult to return to the Eu 5d orbits after being captured by C 2p orbits, leading to the reduction of light energy radiation; the built-in electric field and energy band offsets between g-C 3 N 4 and Sr 2 MgSi 2 O 7 :(Eu,Dy) promote the transfer of photoinduced carriers, which follows a traditional type-II mechanism, resulting in enhanced photocatalytic activity and decreased luminescence-afterglow performance. This paper reveals the relationship between optical-photocatalysis behaviors and the electronic structure of g-C 3 N 4 /Sr 2 MgSi 2 O 7 :(Eu,Dy). It provides a reference for designing and optimizing light-storing assisted photocatalytic composites.
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.
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