Well-dispersed nebula-like ZnO/CeO₂@HNTs heterostructure for efficient photocatalytic degradation of tetracycline

A series of nebula-like ZnO/CeO₂@HNTs heterostructure photocatalysts were synthesized via a novel one-step wet-calcination method for degradation of tetracycline (TC) under simulated solar irradiation. TEM, HRTEM, XRD, FT-IR, XPS, DRS, PL, PC, EIS and ESR techniques were applied for characterization of samples. And the potential structure of new photodegradation products was studied by HPLC–MS analysis. The characterization results revealed the enhanced photocatalytic activity of ZnO/CeO₂@HNTs heterostructure photocatalysts due to the delayed recombination of photogenerated electron-hole pairs. Moreover, surface oxidation state analysis demonstrates that Ce³⁺ and Ce⁴⁺ states coexist in CeO₂, which enhance the separation of electron-hole pairs though cerium oxide shifting between CeO₂ and Ce₂O₃ under photocatalytic process. In addition, the effects of the calcinating temperature, the molar ratio of ZnO to CeO₂ and the dosage of HNTs on photocatalytic activity of ZnO/CeO₂@HNTs heterostructure photocatalysts were researched and the best possible values have been found. Furthermore, the photodegradation mechanism was systematically investigated by active species trapping experiment. It revealed that [Formula presented] radicals play a little role while hole and [Formula presented]₂⁻ are the more major reactive species in the photodegradation process.