Next-Gen Photocatalysts: Solvent-free ZnO-TiO2-g-C₃N₄ Composites for dye degradation and their Antioxidant activity

Abstract This study investigates the photocatalytic performance of Titanium oxide (TiO₂), Zinc Oxide (ZnO), graphitic carbon nitride (g-C₃N₄), and their hybrids for textile effluent degradation. Among these photocatalysts, TiO₂ nanoparticles exhibit a spherical morphology with a particle size ranging from 20 to 50 nm. In contrast, ZnO displays a hexagonal rod-like structure, with an average particle size of 200 nm. The specific surface areas of TiO₂ and ZnO are determined to be 6.413 m²/g and 5.325 m²/g, respectively. ZnO demonstrates slightly lower rhodamine 6G (R6G) degradation efficiency (70.00%) compared to TiO₂ (74.35%), with a rate constant of 0.64 × 10⁻² min⁻¹ and 0.79 × 10⁻² min⁻¹, respectively. g-C₃N₄ exhibits a plate-like morphology with a higher specific surface area (9.018 m²/g) due to its layered structure. The ZnO-5wt.%TiO₂ binary composite shows a specific surface area of 9.098 m²/g and achieves 94.02% degradation of R6G with a rate constant of 1.72 × 10⁻² min⁻¹, highlighting its improved photocatalytic efficiency. Advanced heterojunctions, such as ZnO-5 wt.% TiO₂-10 wt.% g-C₃N₄, have an even greater surface area (9.168 m²/g) and photocatalytic activity, achieving 99.99% degradation of R6G with a rate constant of 2.163 × 10⁻² min⁻¹. The photocatalytic activity of the composite is three times higher than that of pure ZnO. These results highlight the synergistic effects of combining TiO₂, ZnO, and g-C₃N₄, which facilitate reduced electron-hole recombination, enhanced charge carrier separation, and improved photocatalytic degradation efficiency. These findings emphasize the potential of TiO₂, ZnO, g-C₃N₄, and their composites as efficient, cost-effective, and environmentally friendly photocatalysts for textile effluent degradation.