Facile synthesis and enhanced photocatalytic activity of a novel FeVO4/Bi4O5Br2 heterojunction photocatalyst through step-scheme charge transfer mechanism

Abstract

Construction of a step-scheme (S-scheme) heterojunction photocatalyst is currently under investigation as it is known to facilitate a decrease in the e – /h + recombination rate and preserves a strong redox ability. This research work has reported on the use of microwave irradiation combined with the wet impregnation synthesis of FeVO 4 /Bi 4 O 5 Br 2 heterojunctions at different weight percentages (%wt) of FeVO 4 (0.5%, 1%, 3% and 5%wt). The visible-light-driven photocatalytic activities for the photoreduction of Cr(VI), and the decontamination of certain organic pollutants (bisphenol A; BPA, rhodamine B; RhB, and tetracycline hydrochloride; TC) were also investigated. Ethylene glycol that was used as a reaction medium in the microwave synthesis process played a key role in the formation control of a flower-like structure of bismuth-rich Bi 4 O 5 Br 2 . Among the heterojunction photocatalysts, FeVO 4 /Bi 4 O 5 Br 2 with 1%wt of FeVO 4 markedly maximized the photocatalytic activity. Specifically, 95% of Cr(VI) was reduced by a reduction rate that was 6.0 times higher than that of Bi 4 O 5 Br 2 . Similarly, this photocatalyst was able to degrade 90%, 97%, and 88% of BPA, RhB, and TC at degradation rates that were 2.0, 1.2, and 1.6 times higher than Bi 4 O 5 Br 2 , respectively. Trapping experiments indicated that •O 2 − and h + were the main active species responsible for the organic pollutant degradation, while •OH played a minor role in this process. These outcomes were confirmed with the use of the nitrotetrazolium blue transformation method and the terephthalic acid photoluminescence probing technique. Enhancement in the photo-activity of 1%wt-FeVO 4 /Bi 4 O 5 Br 2 was attributed to the extended visible-light absorption range as well as the efficient generation, separation, and migration of photo-generated charge carriers through the S-scheme charge transfer mechanism which was supported by the results from the trapping experiments, XPS and UV–vis DRS analyses, Ag and PbO 2 photo-deposition experiments, and electrochemical studies, along with the consideration of the reduction potentials of reactive oxygen species. • Novel FeVO 4 /Bi 4 O 5 Br 2 catalyst for Cr(VI) reduction and organic pollutant degradation. • Ethylene glycol played a key role in the formation of flower-like Bi 4 O 5 Br 2 structure. • Activity of Bi 4 O 5 Br 2 promoted with optimum content of FeVO 4 coupling (1%wt). • This FeVO 4 /Bi 4 O 5 Br 2 nanocomposite displayed excellent recyclability and stability. • Improved activity was ascribed to S-scheme charge transfer mechanism.