Long-lasting CaAl2O4:Eu2+,Nd3+ phosphor-coupled g-C3N4 QDs composites for the round-the-clock photocatalytic methyl orange degradation

Abstract Long-lasting phosphors are a type of important materials that can release their stored energy in form of light after tuning off the excitation light source. Due to this unique luminescent property, combining a long-lasting phosphor and a suitable photocatalyst can keep the photocatalytic activity in the absence of the excitation light source. Here, a novel round-the-clock photocatalyst, combined the CaAl2O4:Eu2+,Nd3+ (CAOED) blue long-lasting phosphor with the g-C3N4 quantum dots (QDs), is reported for the first time. Our results reveal that when the excitation light is off, the photocatalytic degradation of methyl orange (MO) in the CAOED-coupled g-C3N4 QDs composites can continue for > 3 h, and come back its initial state after several time. Although the light intensity emitted from the CAOED is decreased with the increase of the delay time, the stored energy of the obtained photocatalyst can be recharged and recovered basing on the long-lasting decay curve, exhibiting the round-the-clock behavior. Our discussion reveal that this external irradiation-free photocatalytic activity is due to the long-lasting luminescence of the CAOED caused by the crystal lattice defects and the visible-light utilization and recombination rate of photo-generated carriers in the CAOED-coupled g-C3N4 QDs photocatalyst.