In-situ deposition of Ag and AgFeO2 on Bi2WO6 nanosheet for enhancing visible-light-driven photocatalysis toward degradation of tetracycline

Abstract

A series of novel ternary Bi2WO6/Ag/AgFeO2 composites were successfully prepared by in-situ deposition AgFeO2 onto Bi2WO6 nanosheets, followed by reduction of Ag+ to Ag0 on the surface of Bi2WO6/AgFeO2 via ultrasound-assisted reduction process. The structural characterizations revealed that Ag0 and AgFeO2 was loaded on the smooth surface of Bi2WO6 nanosheets, forming a tightly contact interface. Meanwhile, Bi2WO6 nanosheets as substrates suppressed the aggregation of AgFeO2 nanoparticles. Bi2WO6/Ag/AgFeO2 composites achieved full-spectrum absorption of visible light due to the formation of p-n heterojunction between the Bi2WO6 and AgFeO2 interface and the local surface plasmon resonance (LSPR) of Ag0, as confirmed by UV–vis DRS. Photoelectrochemical results indicated that the formation of both p-n heterojunction and the noble Ag0 improved the separation efficiency of photogenerated electrons and holes. Photocatalysis performance of Bi2WO6/Ag/AgFeO2-80 composite showed that a removal rate of 92.4 % for tetracycline hydrochloride (TC-HCl) under visible light irradiation within 120 minutes, with a kinetic constant 0.01743 min-1, which was 20 times, 15 times, and 3 times higher than that of AgFeO2, Ag/AgFeO2 and Bi2WO6, respectively, and the composite exhibited excellent stability in the fourth cycle experiment. The radical capture experiments proved that superoxide radicals (⸱O2-) play a major role in the degradation process, and the holes (h+) as the second active species. Based on the above results and in situ XPS, a possible electron transfer pathway was proposed.