Enhanced visible light photocatalytic activity of ZnO doped with down-conversion NaSrBO₃:Tb³⁺ phosphors

ZnO-NaSrBO₃:Tb³⁺ (ZNT) composites were successfully synthesized via microwave-assisted reaction of the ZnO precursor with a NaSrBO₃:Tb³⁺ suspension using a microwave synthesis system. The morphology, structure and photocatalytic performance in the degradation of methylene blue (MB) were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, UV-vis absorption spectroscopy, fluorescence spectrophotometry and electrochemical impedance spectroscopy, respectively. The results show that the ZNT composites exhibit enhanced photocatalytic activity in the degradation of MB with a maximum degradation rate of 97% under visible light irradiation compared with pure ZnO (12%), which is ascribed to the increased light absorption and the reduction of photoelectron-hole pair recombination in ZnO with the introduction of NaSrBO₃:Tb³⁺, as well as the light down-converting effect of NaSrBO₃:Tb³⁺, which facilitates the self-sensitized degradation of MB.