A series of CuOx-decorated ZnFe2O4 samples were prepared by a hydrothermal method and investigated as a catalyst for the photocatalytic and Fenton-like degradation of Orange II. The active species and catalyst active sites in the two processes were also studied. It was found that the introduced CuOx significantly enhanced the photocatalytic and Fenton-like performance of ZnFe2O4. Especially, ZnFe2O4-Cu3 prepared with the Cu/Zn ratio of 3:7 exhibited a very high Fenton-like activity in the pH range 5-9. The enhanced photocatalytic activity of ZnFe2O4-Cu3 could be because the formed ZnFe2O4/Cu2O heterojunction improved the separation efficiency of the photogenerated carriers. The photogenerated hole was responsible for Orange II degradation. As for the Fenton-like reaction, •O2- was the active species, and the surface ≡Cu2+ with a higher redox ability should be the active site for H2O2 activation despite its lower surface content than that of ≡Cu+, ≡Fe2+, and ≡Fe3+. Finally, a possible pathway for Orange II degradation was proposed according to the liquid chromatography-mass spectrometry result.
Keywords: CuOx; Fenton; ZnFe2O4; active species; photocatalysis.