Synthesis and characterization of ternary NiO@Bi2MoO6–MoS heterojunction with enhanced photodegradation efficiency towards indigo carmine dye

Abstract

Heterojunctions and metal oxide dopants are commonly used in binary and ternary nanocomposites to enhance photo degradability and maintain metal-free properties. This work describes the preparation of a novel NiO@Bi2MoO6–MoS complex ternary heterostructure using a simple solvothermal technique that possesses excellent photo activities for the removal of toxic Indigo carmine (InCa) dye from wastewater using a visible-illumination source. The prepared composites were characterized using various physicochemical techniques such as UV–Visible spectra, X-ray diffraction (XRD) techniques, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transforms infrared (FTIR) spectroscopy, elemental disperse X-ray (EDX) analysis, BET surface area, photoluminescence (PL), electron spin resonance (ESR) spectroscopy, and LC-MS analysis. The UV–Visible spectrophotometer confirmed that the absorption performance of the ternary NiO@Bi2MoO6–MoS composite is comprehensive in the visible light regions. NiO@Bi2MoO6–MoS exhibited the characteristic diffraction peaks of NiO and Bi2MoO6–MoS with a band gap energy (Eg) of 3.03 eV. SEM images confirmed that the synthesized composites show good phase confirmation, with particle sizes of ∼25 nm and morphologies of nanoflakes (Bi2MoO6–MoS) and nanorods (NiO@Bi2MoO6–MoS). The PL intensity of NiO@Bi2MoO6–MoS is much lower than that of Bi2MoO6 and Bi2MoO6–MoS composites, indicating a much more effective separation of photo-generated electrons and holes at the interface which in turn leads to the expected photocatalytic performance. The photocatalytic activity results showed that the degradation efficiency of NiO@Bi2MoO6–MoS for InCa dyes was 98.8%within 120 min, which is significantly superior to the binary composite Bi2MoO6–MoS (73.2%).The enhanced photo degradability of NiO@Bi2MoO6–MoSis a result of the hierarchical superstructure, enhanced visible light absorption, efficient charge transfer, and synergistic interaction between NiO, MoS, and Bi2MoO6 nanoparticles. Synergistic adsorption, effective double Z-scheme, and S-scheme mechanisms were efficient for the degradation of InCa dye into CO2, H2O, inorganic ions, and simpler products that showed excellent recyclability over five consecutive cycles.