Hybridization of silver orthophosphate with a melilite-type phosphor for enhanced energy-harvesting photocatalysis

In this study, a silicate-based water-resistant melilite-type (Sr2MgSi2O7:Eu2+,Dy3+) long-lasting phosphor (LLP) was hybridized with silver orthophosphate (Ag3PO4), a typical visible-light active photocatalyst, by a facile solution mixing approach to achieve enhanced energy-harvesting photocatalysis. The structure of the composites was characterized by XRD, FT-IR, XPS and SEM and the effect of hybridization on both solar/visible light and afterglow photocatalysis was examined. Ag3PO4 nanocrystals with a size of ∼900 nm were found to be highly dispersed and localized on the surface of the tetragonal melilite crystal in the hybridized material. Photoluminescence and long-lasting luminescence of the LLP were weakened due to the absorption or light filtering effect caused by the deposited Ag3PO4. Hybridization of Ag3PO4 with the LLP formed a new charge-transfer structure evidenced by the ESR and photocurrent responses, and increased the solar and visible-light photoactivity by 2–2.5 fold. The LLP could absorb and store photon energy ranging from the visible light to ultraviolet region and transform this energy to an afterglow photon emission at 470 nm (∼2.6 eV), which further drove 32% of the retained methyl orange to be degraded after light-off. These results demonstrate that the hybridization of the melilite-type LLP and Ag3PO4 can greatly enhance photocatalysis under light illumination and produce a meaningful afterglow photodegradation effect after illumination extinction.