Solvothermal Synthesis of g-C₃N₄/TiO₂ Hybrid Photocatalyst with a Broaden Activation Spectrum

A solvothermal self-made composite of graphitic carbon nitride (g-C₃N₄) and commercially available titanium dioxide (TiO₂) demonstrated the removal of commercial acid green-25 (AG-25) textile dye in a saline water matrix when activated by ultraviolet (UV) and visible light. The g-C₃N₄-TiO₂ composite was characterized by X-ray diffraction (XRD), Nitrogen sorption–desorption recording and modeling by the Brunauer–Emmett–Teller (BET) theory, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and electron spin resonance (ESR). The solvothermal process did not modify the crystalline structure of the g-C₃N₄ and TiO₂ but enhanced the surface area by interlayer delamination of g-C₃N_4. Under a simulated solar spectrum (including UVA/B and vis wavelengths), the degradation rate of AG-25 by the composite was two and four times higher than that of TiO₂ and pure g-C₃N₄, respectively (0.04, 0.02, and 0.01 min⁻¹). Unlike TiO_2, the g-C₃N₄-TiO₂ composite was activated with visible light (the UV portion of the solar spectrum was filtered out). This work provides insight into the contribution of various reactive oxidative species (ROS) to the degradation of AG-25 by the composite.