Fabrication of Ag/AgBr/Ag3VO4 composites with high visible light photocatalytic performance

Abstract

Herein, Ag/AgBr/Ag₃VO₄ composites were synthesized by a simple continuous precipitation method. The obtained composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy and photoluminescence spectroscopy (PL). Photocatalytic performance of the composites was assessed by the degradation of methyl orange (MO) and tetracycline hydrochloride (TC) under visible light, and the effects of different nominal mass ratios of AgBr and Ag₃VO₄ on the photocatalytic activity were investigated. The results showed that after 20 min of visible light irradiation (λ > 420 nm), the removal rate of MO in the presence of a 5 : 1 sample reached 98.6%. The EIS and photocurrent results demonstrated that the enhancement of the visible light photocatalytic activity was attributed to the efficient electron-hole pair separation. In addition, the scavenging reactions conducted via the addition of different scavengers confirmed that h⁺ and ·O^2- were the main active species in the reaction. The present study offers potential for the degradation of contaminants.

Fig. 1. Schematic of the synthesis route of the Ag/AgBr/Ag₃VO₄ composites.

Fig. 2. (a) XRD patterns of Ag/AgBr and Ag/AgBr/Ag₃VO₄ composites and (b) pure Ag₃VO₄.

Fig. 3. (a) Survey XPS spectra of the S2 sample; (b, c, d and e) high-resolution XPS data of Ag 3d, Br 3d, V 2p, and O 1s for S2, respectively.

Fig. 4. SEM images of (a) pure Ag/AgBr, (b) pure Ag₃VO₄, and (c and d) S2 sample; (e and f) EDS spectra of pure Ag/AgBr and S2 sample, respectively.

Fig. 5. (a) UV-vis diffuse reflectance spectra of Ag/AgBr, Ag₃VO₄ and Ag/AgBr/Ag₃VO₄ composites; (b) Tauc plot of Ag/AgBr, Ag₃VO₄ and S2.

Fig. 6. PL spectra of pure Ag/AgBr, Ag₃VO₄ and S2 sample.

Fig. 7. (a) Electrochemical impedance spectra of Ag/AgBr and S2 photocatalysts and (b) transient photocurrent response of Ag/AgBr and S2.

Fig. 8. (a) The photocatalytic degradation of MO via different as-synthesized photocatalysts; (b) the photocatalytic degradation of TC via different as-synthesized photocatalysts; (c) pseudo first-order plot of the photocatalytic degradation of MO via different as-synthesized photocatalysts; (d) change of TOC removal rate of MO in the presence of the S2 sample.

Fig. 9. (a) Reusable performance of S2 and (b) XRD data contrast diagram before and after the use of S2.

Fig. 10. Photocatalytic degradation of MO in an aqueous solution via S2 under different conditions.

Fig. 11. The possible photocatalytic mechanism of the Ag/AgBr/Ag₃VO₄ composites.