Superior photocatalytic and electrochemical activity of novel WS2/PANI nanocomposite for the degradation and detection of pollutants: Antibiotic, heavy metal ions, and dyes

The untreated discharge of noxious pollutants is drawing worldwide concern due to their irretrievable damage to the environment. Especially, pharmaceutical waste has been identified as an emerging pollutant due to its increased demand and untreated discharge into the water bodies. The elimination and detection of such persistent contaminants from wastewater have proven to be a difficult endeavor due to the constraints imposed by the materials and technologies. Therefore, in the present work "free two birds with one key" strategy was implemented to develop a novel visible-light-driven photocatalyst and the electrochemical sensor using WS2/PANI nanocomposite for the degradation and detection. The synthesized WS2/PANI nanocomposite was systematically characterized with a High-resolution transmission electron microscope (HRTEM) and Field emission scanning electron microscope (FESEM) for morphology, Energy-dispersive X-ray (EDX) spectroscopy for elemental analysis, X-ray diffractogram (XRD) for orientation planes, Fourier transform infrared (FTIR) spectroscopy for functional groups and bonds, Zeta potential for the surface charge, Tauc's plot for bandgap analysis, Photoluminescence (PL) spectroscopy study for defects, Time-Resolved Photoluminescence (TRPL) for photogenerated charge carriers, BET for surface parameters and Liquid chromatography-mass spectrometry (LC-MS) for intermediate photodegradation products. The WS2/PANI nanocomposite displayed excellent activity for the photodegradation of antibiotic (nitrofurantoin: NFT, 95%) along with the detection and also degraded textile dye (Methyl orange: MO, 97%), and heavy metal ion (Cr(VI), 99%) with good reusability up to 4 cycles. The superior photocatalytic activity demonstrated by WS2/PANI attributes to its remarkable properties such as a high photoinduced charge separation (5.76 ns) and visible-light-driven bandgap (2.6 eV). A scavenger experiment was also performed to confirm the formation of photoinduced reactive oxygen species (•OH and O2•−). In addition to photocatalytic degradation, WS2/PANI nanocomposite portrayed excellent electrochemical detection of NFT with a low limit of detection (LOD) of 0.01 µM and a wide linear range of 500–0.01 µM.