Citric acid-capped NiWO4/Bi2S3 and rGO-doped NiWO4/Bi2S3 nanoarchitectures for photocatalytic decontamination of emerging pollutants from the aqueous environment

Abstract

Herein, we describe the successful synthesis of NiWO4/Bi2S3 and reduced graphene oxide (rGO-NiWO4/Bi2S3) nanocomposites through a simple green sol-gel approach. The fabricated composites were subsequently characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy Dispersive X-Ray Analysis (EDX) and ultraviolet–visible spectroscopy (UV-VIS) spectroscopic analyses. Dielectric properties were done by a precision impedance analyzer. Tanδ and dielectric constant for NiWO4/Bi2S3 and rGO-NiWO4/Bi2S3 were 1.811, 292818, and 0.2970, 344574, respectively, at 20 Hz. The photocatalytic performance of NiWO4/Bi2S3 and rGO-NiWO4/Bi2S3 was investigated against methylene blue and methyl orange dyes in an aqueous medium. NiWO4–Bi2S3 showed degradation of methylene blue 15.52% after 20 min, 21.8% after 30 min and 46.8% after 40 min. Similarly, for methyl orange dye it was 18.1% after 20 min, 54% after 30 min and 59.36% after 40 min. Compared to NiWO4/Bi2S3, rGO-NiWO4/Bi2S3 exhibited superior degradation efficiency of 7.5% (20 min), 25.24% (30 min) and 57.71% (40 min) for methylene blue, and 35.7% (20 min), 56.98% (30 min) and 72.42% (40 min) for methyl orange under sunlight. This enhancement in photocatalytic and dielectric properties might be attributed to the presence of graphene in rGO-NiWO4/Bi2S3 nanococomposite. Different factors such as effect of time, pH, dose of catalyst, concentration of dye were optimized and the reusability of superior catalyst rGO-NiWO4/Bi2S3 was also checked for four cycles. In conclusion, promising photocatalytic and dielectric properties of rGO-NiWO4/Bi2S3 suggest its potential applications in the photocatalytic degradation of organic pollutants and energy storage materials. This study provides a well-developed route to exploit metal sulphide/oxide nanocomposites in environmental remediation and energy storage devices.