The GO/Bi₂O₃/WO₃ ternary hybrid composite as an efficient sunlight-driven heterogeneous photocatalyst for wastewater remediation

Semiconductor photocatalysts with engineered heterostructure are gaining attention for environmental remediations. The combination of two or more metal oxides with support materials has proved an effective strategy for better charge separation to lead to redox reactions. Therefore, the novel combination of tungsten oxide (WO₃) and bismuth oxide (Bi₂O₃) with graphene oxide (GO) was studied to degrade methylene blue dye as a model organic pollutant. The novel composite material was synthesized using a facile hydrothermal route. The photocatalysts (i.e., WO₃, WO₃/Bi₂O₃, and GO/WO₃/Bi₂O₃ composite) were characterized in terms of surface morphology by scanning electron microscope, elemental mapping by energy-dispersive X-ray, crystalline structure by X-ray diffraction, and functional group identification by Fourier transform infrared spectroscopy. The characterization analysis confirms the successful synthesis of all pristine and composite materials. The optical response of photocatalysts (WO₃/Bi₂O₃) and composites photocatalyst (GO/WO₃/Bi₂O₃) was checked by UV–visible spectroscopy using the Tauc plot method. The considerable reduction in energy bandgap from 2.9 (for WO₃/Bi₂O₃) to 2.2 (for GO/WO₃/Bi₂O₃) suggests that the proposed composite material is not only effective under natural sunlight but also a potential material with improved charge separation. The optimization of influencing parameters was done, and the best degradation efficiency of about 98% was achieved under pH = 9, composite dose = 30 mg per 100 mL, and H₂O₂ concentration = 13 mM, with the reaction time of 180 min under ambient sunlight. Kinetic studies confirmed that the photocatalytic degradation process followed the 1st-order kinetic model. The response surface methodology (RSM) was employed to analyze the data statistically.