Fabrication of graphitic carbon nitride synthesized via pyrolysis for environmental remediation: a detailed experimental analysis with different parametric optimizations

Abstract

This paper reports on the photodegradation of the Rh 6G dye using a g-C₃N₄ (g-CN) nanosheet photocatalyst under UV light irradiation. The g-C₃N₄ nanosheets were synthesized using a simple pyrolysis method at 450 °C for 3 h at a heating rate of 2 °C min⁻¹. Their structural phase, functional groups, surface area, optical properties, elemental composition, and morphology were investigated via XRD, BET, UV-vis, photoluminescence spectroscopy, X-ray photoelectron spectroscopy, energy dispersive spectroscopy, and SEM microscopy. The tri-s-triazine structure of g-C₃N₄ was confirmed and the crystal size was calculated to be 5 nm. g-C₃N₄ displayed a nanosheet morphology with a BET surface area of 8 m² g⁻¹. C–N stretching and s-triazine units were observed in the FTIR spectrum. The photoluminescence (PL) emission maximum at 432 nm provided band edge emission related to a band gap of 2.9 eV, and the PL lifetime was 7.6 ns, which is reasonably high for photocatalytic application. Through the C1s XPS spectrum, sp²-hybridized carbon linkages of N–CN in the aromatic skeleton rings, such as triazine or heptazine rings, of g-C₃N₄ were found. The photocatalytic characteristics of g-C₃N₄ were studied with the Rh-6G dye using UV light illumination. Initially, the Rh-6G dye concentration and catalyst (g-C₃N₄) loading were optimized for the best dye degradation at 0.01 mmol and 50 mg, respectively. The maximum efficiency of g-C₃N₄ was 99.6% degradation of the Rh-6G dye in 300 minutes. Lower charge-transfer resistance was found to be the reason for the enhanced photodegradation activity. The most dominant reactive species that participated in the light-activated reaction were superoxide radicals. The influence of pH on photodegradation was studied and the photocatalyst was found to perform better in an acidic pH range. In addition, g-C₃N₄ was structurally stable, highly recyclable, and, therefore, could be reused in many cycles of photocatalysis.