Preparation and photocatalytic performance of a magnetically recyclable ZnFe2O4@TiO2@Ag2O p-n/Z-type tandem heterojunction photocatalyst: Degradation pathway and mechanism

Abstract

The high recombination rate of photoelectron-hole pairs and the difficulty separating the catalyst from the solution severely restrict the development of photocatalysis. The construction of heterojunctions and the loading of magnetic carriers are considered to be effective solutions to these two problems. Against this background, a magnetically recoverable ZnFe2O4 @TiO2 @Ag2O heterojunction composite photocatalyst was prepared. Under the optimum preparation conditions, the degradation rate of rhodamine B (RhB) by the composite catalyst under ultraviolet(UV) light reached 98.4% within 40 min; the kinetic constant k was 0.09449 min−1, which was 39.2, 2.0 and 7.8 times those of ZnFe2O4, TiO2 and Ag2O alone, respectively, and the removal rate of total organic carbon (TOC) reached 63.2%. In addition, the catalyst also showed good magnetic recovery performance and reusability. A series of characterization and mechanism research results show that the excellent photocatalytic performance is due to the synergistic effect of the Z-type heterojunction and p-n junction, which promotes the separation and transfer efficiency of photogenerated electron-hole pairs. In conclusion, this work provides new insight into the preparation of magnetically recoverable heterojunction photocatalysts and their application in the degradation of organic pollutants.