A facile two-step hydrothermal preparation of 2D/2D heterostructure of BiWO/WS for the efficient photodegradation of methylene blue under sunlight.

A facile two-step hydrothermal method was successfully used to prepare a photocatalyst BiWO/WS heterojunction for methyl blue (MB) photodegradation. Fabricated photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). Band gap measurements were carried out by diffuse reflectance spectroscopy (DRS). Results indicated that the prepared heterostructure photocatalyst has increased visible light absorption. Photocatalytic performance was evaluated under sunlight irradiation for methylene blue (MB) degradation as a model dye. Variations in pH (4-10), amount of catalyst (0.025-0.1 g/L), and initial MB concentrations (5-20 ppm) were carried out, whereas all prepared catalysts were used to conduct the tests with a visible spectrophotometer. Degradation activity improved with the pH increase; the optimum pH was approximately 8. Catalyst concentration is directly related to degradation efficiency and reached 93.56% with 0.075 g of the catalyst. Among tested catalysts, 0.01 BiWO/WS has exhibited the highest activity and a degradation efficiency of 99.0% in 40 min (min) for MB. MB photodegradation follows pseudo-first-order kinetics, and obtained values of k were 0.0482 min, 0.0337 min, 0.0205 min and 0.0087 min for initial concentrations of 5 ppm, 10 ppm, 15 ppm, and 20 ppm, respectively. The catalyst was reused for six cycles with a negligible decrease in the degradation activity. Heterostructure 0.01 BiWO/WS has exhibited a photocurrent density of 16 μA cm, significantly higher than 2.0 and 4.5 μA cm for the pristine WS and BiWO, respectively. The findings from these investigations may serve as a crucial stepping stone towards the remediation of polluted water facilitated by implementing such highly efficient photocatalysts.