Structural, optical, and photocatalytic properties of graphitic carbon nitride

Graphitic carbon nitride (g-C₃N₄) was synthesized via a simple calcination method using melamine and thiourea precursors, and its structural, optical, and photocatalytic properties were investigated. X-ray diffraction confirmed the formation of g-C₃N₄, with a characteristic (002) peak at 27.3°. The crystallite size of thiourea-derived g-C₃N₄ (T-GCN, 4.12 nm) was slightly smaller than that of melamine-derived g-C₃N₄ (M-GCN, 4.67 nm). UV–Visible spectroscopy revealed a slight reduction in the optical band gap of T-GCN (2.92 eV) relative to M-GCN (2.99 eV). FTIR spectroscopy indicated the presence of triazine rings and nitrogen-containing functional groups. Scanning electron microscopy showed agglomerated morphology in both samples. X-ray photoelectron spectroscopy confirmed the presence of C and N, with T-GCN exhibiting a slightly higher nitrogen content. Thermogravimetric analysis demonstrated enhanced thermal stability for T-GCN. Under visible light irradiation, T-GCN exhibited superior photocatalytic activity, achieving 81.72 % and 84.91 % degradation of crystal violet and malachite green dyes, respectively, compared to 70.18 % and 77.09 % for M-GCN. This enhanced performance is attributed to the higher surface area (17.56 m²/g) and pore volume (6.59 × 10^–2 cc/g) of T-GCN, which facilitates improved light absorption and charge-carrier transport.