Long afterglow phosphor driven g-C3N4 photocatalyst for continuous water purification under light and dark conditions

An important issue in photocatalysis is the light required to carry out the catalytic reaction, so maintaining photocatalytic reaction activity in the dark has been the ultimate target of expanding photocatalytic technology. Herein, we report a photocatalyst g-C3N4/SrAl2O4:Eu2+,Dy3+ through a strategy that couples the energy-storing and light-releasing properties of long afterglow materials and the light-absorbing properties of photocatalytic materials. g-C3N4/SrAl2O4:Eu2+,Dy3+ is able to effectively degrade methyl orange in water under visible light using molecular oxygen in the air, but it maintains significant methyl orange degradation activity after the light is turned off, as if SAO acts as a built-in light source in it. The photocatalytic degradation mechanism is investigated by active species capture experiments, which shows that superoxide radicals (•O2−), hydroxyl radicals (•OH), holes (h+), and singlet oxygen (1O2) generate during the photocatalytic process. Among them, •O2− is the relatively predominantly acting reactive species. This study exemplifies the design of a continuously working photocatalyst with conceptual value for light storage, which provides ideas for practical energy and environmental system applications.