La2O3 media enhanced electrons transfer for improved CeVO4@halloysite nanotubes photocatalytic activity for removing tetracycline

Abstract A series of La2O3/CeVO4@halloysite nanotubes composites were successfully fabricated by the hydrothermal method. The La2O3/CeVO4@halloysite nanotubes composites display outstanding photocatalytic activity for removing tetracycline (TC) solution under visible light irradiation (λ ≥ 420 nm). After irradiation 60 min, an optimized La2O3/CeVO4@halloysite nanotube composite exhibited a high photocatalytic activity (87.1%), which is 3.89 times higher than that of raw CeVO4 (22.4%). The improvement of ternary composites performance is attributed to the Ce3+ and Ce4+ pairs in CeVO4. Besides, constructing heterojunctions between La2O3 and CeVO4 can inhibit the recombination of photoinduced electrons and holes, which is ascribed to the La3+ as electron trap to enhance the charge transfer. According to the trapper experiments and Electron Spin Resonance (ESR) analysis, the h+ and •O2− are major reactive species during the degradation. In addition, the oxygen vacancies are in the ternary photocatalyssts. The photocatalytic degradation intermediates of the solution were identified by High performance liquid chromatography-Mass spectra (HPLC-MS).