Fabrication and efficient visible light photocatalytic properties of novel zinc indium sulfide (ZnIn2S4) - graphitic carbon nitride (g-C3N4)/bismuth vanadate (BiVO4) nanorod-based ternary nanocomposites with enhanced charge separation via Z-scheme transfer

Abstract

Novel ZnIn2S4-g-C3N4/BiVO4 nanorod-based ternary nanocomposite photocatalysts with enhanced visible light absorption were synthesized and systematically characterized to confirm the formation of ZnIn2S4 marigold flowers, the layered structure of the g-C3N4, BiVO4 nanorods, and the formation of binary and ternary nanocomposites. The visible light absorption of BiVO4 was significantly improved after coupling with g-C3N4 and ZnIn2S4, which was confirmed by UV-visible diffuse reflectance spectroscopic analysis. Ternary ZnIn2S4-g-C3N4/BiVO4 nanocomposites exhibited excellent visible light photocatalytic decomposition efficiency (VL-PDE) when used for the degradation of congo red (CR) dye and metronidazole (MTZ) pharmaceutical, as well as excellent stability and reusability. The ternary 5%ZnIn2S4-50%-g-C3N4/BiVO4 nanocomposite showed higher VL-PDE for CR (81.5%) and MTZ (59%) degradation than the binary composites, g-C3N4 and BiVO4. Radical quenching experiments showed that h(+), OH, and O2(-) were the reactive radicals, validating that the Z-scheme charge carrier transfer mechanism was responsible for the enhanced VL-PDE of the ternary ZnIn2S4-g-C3N4/BiVO4 nanocomposites, which was further confirmed by photoluminescence analysis. Furthermore, kinetic studies showed that the degradation followed pseudo-first-order kinetics, and that the ternary photocatalysts could be reused up to three times with good stability. The enhanced visible light absorption, high surface area, high adsorption capacity, Z-scheme charge carrier transfer, and increased lifetime of photo-produced electron-hole pairs were responsible for the increased visible light photocatalytic decomposition efficiency.

Keywords: BiVO(4); Photocatalysis; Ternary nanocomposite; Visible light; Z-scheme transfer; ZnIn(2)S(4); g-C(3)N(4).