The efficient solar-light-driven photocatalytic performance of hybrid reduced graphene oxide/TiO2/graphitic carbon nitride composites for organic pollutant degradation

Accelerated industrial development in recent years has a negative influence on the aquatic ecosystem. Pollutants such as pesticides, microplastics, persistent organic pollutants, and dyes are present. In several industries, including cosmetics, plastic, paper, textiles, and rubber, synthetic dyes are used to give color to the products. The massive scale of used synthetic dyes, which are chemically and thermally stable in water, represents a potential hazard to the environment. The photocatalytic removal/degradation and wastewater treatment under solar-like irradiation have their own limitations. It is necessary to solve major challenges to overcome the drawbacks of the conventional water treatment processes. In this research, the hybridized photocatalyst was successfully synthesized as a mixture of pure TiO2 particles, reduced graphene oxide (rGO), and graphitic carbon nitride (g-C3N4). The graphene oxide (GO) material was synthesized by Hummer's method using natural graphite flakes (particle size ≤ 50 µm). The bulk g-C3N4 was prepared by a simple pyrolysis procedure using urea as a precursor. The hybridised rGO/TiO2/g-C3N4 photocatalyst has been self-assembled through one-pot hydrothermally synthesis followed by an annealing treatment. The morphological and structural analysis of the fabricated photocatalysts have been analyzed by X- ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Photocatalytic experiments with solar-like irradiation were performed to evaluate the efficiency of the synthesized materials. Composites were used as photocatalysts in the degradation of dye Methylene blue (MB) dye in an aqueous medium at a pH of 5.9. In addition to the natural pH of the solution (5.9), four other pH values (3.3, 7.3, 10.5, and 12.5) were adjusted and the efficiency of MB degradation was studied. The synthesized rGO/TiO2/g-C3N4 hybrid shows higher photocatalytic activity than pure TiO2 particles, TiO2/rGO, and TiO2/g-C3N4 composites in the degradation of MB dye in an aqueous medium (10 mg/L) under solar-like irradiation. The obtained results show that the photocatalytic activity of TiO2 increases with a higher amount of added rGO and g-C3N4. The pH of the solution also affects the MB degradation rate. Therefore, the highefficient hybridised rGO/TiO2/g-C3N4 photocatalyst could have the potential for environmental remediation.