Preparation and characterization of sulphur and zinc oxide Co-doped graphitic carbon nitride for photo-assisted removal of Safranin-O dye

Abstract

Recently, there has been significant interest in photocatalytic reactions involving graphitic carbon nitride (g-C₃N₄) due to its sp²-hybridized carbon and nitrogen content and it is an ideal candidate for blending with other materials to enhance performance. Here, we have synthesized and analyzed both doped and undoped g-C₃N₄ nanoparticles. Specifically, we co-doped sulfur (S) into g-C₃N₄, integrated it with ZnO particles, and investigated the photocatalytic potential of these nanocomposites to remove Safranin-O dye. The initial step involved the preparation of pure g-C₃N₄ through calcination of urea. Subsequently, S-g-C₃N₄ was synthesized by calcining a mixture of urea and thiourea with a 3 : 1 ratio. Finally, the ZnO–S-g-C₃N₄ composite was synthesized using the liquid exfoliation technique, with distilled water serving as the exfoliating solvent. These samples were characterized by advanced techniques, including UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray Diffraction (XRD), energy dispersive X-ray (EDX) and scanning electron microscopy (SEM), to assess their crystallinity, morphology, optical properties, and phase purity. Subsequently, these nanocomposites were employed in catalytic and photocatalytic processes to remove the Safranin-O dye (SO). The results highlighted the formation of Z-scheme junction responsible for ZnO–S-g-C₃N₄'s significant performance improvement. The comparison of results demonstrated that S-g-C₃N₄ and ZnO–S-g-C₃N₄ composites revealed an effective removal of Safranin-O dye in the presence of UV-light as compared to pure g-C₃N₄, as it was attributed to the phenomenon of improved separation of photogenerated charge carriers as a result of heterojunction formation between S-g-C₃N₄ and ZnO interfaces. In addition to improving photocatalytic performance, this study presents a facile route for producing ZnO–S-g-C₃N₄ composite with superior adsorption capabilities and selectivity.