Thermal Polymerisation Synthesis of g-C3N4 for Photocatalytic Degradation of Rhodamine B Dye under Natural Sunlight

The photocatalytic performance of g-C3N4 materials prepared by different precursors for Rhodamine B (RhB) dye degradation was studied. Their crystal structure, morphologies, chemical compositions, functional groups, and optical and photoelectrochemical performances of prepared g-C3N4 were analysed and characterised using X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV-Vis diffuse reflectance spectra, photoluminescence, and electrochemical workstations. The degradation of RhB dye in the presence of visible light and sunlight was utilised to assess the photocatalytic efficiency of the g-C3N4 photocatalyst. The results of the photocatalytic comparison experiment showed that the g-C3N4 photocatalyst prepared with urea as a precursor (UCN) has the best photocatalytic performance, achieving 99.61% removal in 40 min. In addition, the photocatalyst UCN can completely degrade 10 mg/L RhB dye within 20 min under sunlight, demonstrating its potential for practical applications under natural sunlight conditions. After four cycles, the degradation rate remains above 99%, demonstrating excellent stability and reusability. Due to its lower average pore number, larger BET-specific surface area and volume of pores, UCN provides more activity spaces and facilitates the adsorption of pollutant molecules, thereby enhancing photocatalytic activity. It was established through the active substance trapping studies that the main reactive species involved in the photocatalytic degradation process of RhB dye is •O2−. This study showed that g-C3N4 synthesised with urea as the precursor has better photocatalytic performance in the degradation of RhB dye.