Superior photocatalytic activity of tungsten disulfide nanostructures: role of morphology and defects

Tungsten disulphide (WS2) nanostructures, WS2 nanosheets (W-NS) and WS2 nanorods (W-NR), were synthesized by varying the surfactant, N-cetyl-N, N,N-trimethyl ammonium bromide (CTAB), concentration using facile hydrothermal technique. Samples were characterized by high-resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM) for morphology, X-ray diffraction (XRD) to confirm their phase and crystal structure, photoluminescence (PL) and Raman studies for the determination of defect density, Tauc plot for the determination of band gap, Fourier transform infra red (FTIR) spectroscopy for functional groups and bonds, and Brunauer-Emmett-Teller (BET) isotherms for the determination of pore size and surface area. A comparative study using WS2 nanostructures (W-NS and W-NR) was conducted to observe the photocatalytic degradation efficiency (n) and degradation kinetics on methylene blue (MB) and 4-chlorophenol (4-CP). The superior photocatalytic performance of W-NS over W-NR is attributed to enhanced pore size and reduced defect density. High-performance liquid chromatography was carried out for the determination of intermediate products during photocatalytic degradation.