Construction of magnetically separable novel arrow down dual S-scheme ZnIn2S4/BiOCl/FeVO4 heterojunction for improved photocatalytic activity

Abstract

• ZnIn 2 S 4 /BiOCl/FeVO 4 ternary heterojunction synthesised by facile co-precipitation method. • The ternary heterojunction was meticulously characterised and studied. • Improved light absorption, redox capability, and easy magnetic separation. • Decolourised 98% of 10ppm solution of RhB in 30 minutes with excellent photostability. • Dual S-Scheme mechanism of charge transfer. The dual S-scheme ZnIn 2 S 4 /BiOCl/FeVO 4 heterojunction was synthesized as it can promote carrier separation while enhancing redox capability. The XRD results indicated the synthesis of pure ZnIn 2 S 4 , BiOCl, and FeVO 4 and the presence of peaks corresponding to these semiconductors in the ternary nanocomposite. The FTIR and XPS investigations confirmed these findings and revealed a change in structural characteristics because of strong heterogeneous contact at the surface. The improved light absorption in the construction of binary and ternary composite was confirmed by UV-Vis spectroscopy. Electrochemical impedance spectroscopy confirmed reduced resistance at the interface and better charge separation. The faster interfacial transport was found, and lower photogenerated charge recombination was found for ternary photocatalysts using the EIS Nyquist plot and the photoluminescence spectrum. The RhB degrading efficiency order was found to be ZnIn 2 S 4 /BiOCl/FeVO 4 > BiOCl/FeVO 4 > FeVO 4 > BiOCl > ZnIn 2 S 4 . The ternary photocatalyst ZnIn 2 S 4 /BiOCl/FeVO 4 decolorized RhB almost completely (98%) in 30 min, and COD studies showed 71.2% of RhB completely degraded under simulated solar radiations. GC-MS spectra for samples drawn from the reaction over time validated the results. The ternary composite has the highest rate constant value (0. 0.12415 min -1 ), which is 13.42, 10.70, 11.04, and 5.30 times more than ZnIn 2 S 4 , FeVO 4 , BiOCl, and BiOCl/FeVO 4 , respectively. Radical scavenging studies confirmed reactive oxidizing species, • OH, • O 2 -, and h + , and validated the proposed dual S-scheme charge transfer mechanism. Moreover, ternary photocatalyst can be reused four times with high photocatalytic stability.