Performance and mechanism of photocatalytic degradation of tetracycline by Z–scheme heterojunction of CdS@LDHs

Abstract Z–scheme heterojunction has the advantages of high carrier separation efficiency and strong oxidation ability, which is a potential material for photodegradation. In this paper, CdS@Zn,Cr-layered double hydroxides (CdS@LDHs) Z–scheme heterojunction was synthesized and used for photocatalytic degradation of tetracycline (TC). The effects of the amount of catalyst, pH value of the solution, initial concentration of TC, light intensity, and reaction temperature were studied. The degradation kinetics and mechanism were also discussed in detail. Under the optimal conditions (initial concentration of TC 50 mg/L, pH 9, light intensity 500 W, the amount of the catalyst 25 mg, and reaction temperature 45 °C), the highest removal percentage and the corresponding activity of CdS@LDHs was 93.04% and 37.09 mg g−1 h−1, respectively. In addition, DFT calculation confirmed the existence of built–in electric field (BIEF) in the heterojunction, which promotes the electron transfer from CdS to LDHs. The amount of electron transfer was accelerated, and the recombination of electron and hole was obviously inhibited, so that they were more involved in oxidation and reduction. Thus, it makes CdS@LDHs heterojunction as a highly efficient catalyst for photodegradation of TC.