Photocatalytic activity mechanism of oxygen vacancy saturated blue WO3-x / exfoliated g-C3N4 Z-scheme heteronanostructures

• Fabrication of g-C 3 N 4 /WO x heteronanostructures through the Copolycondensation growth process. • Utilizing highly oxygen vacancy deficient blue WO 3-x for enhanced photocatalytic activity. • Z-scheme mechanism followed for MB dye degradation. • 93 % MB removal within 30 min of visible light irradiation. • OH and holes as dominant reactive species for MB removal. In this research, g-C 3 N 4 /WO 3-x nanostructures were synthesized through the polycondensation of urea in the presence of blue WO 3-x nanoparticles synthesized by arc discharge in water. This sequential synthesis approach has a direct impact on the interfacial junction between the highly activated surfaces of the blue WO 3-x nanoparticles(WOx), characterized by a heavily oxygen-defected structure, and the two-dimensional g-C 3 N 4 nanosheets (GCN). This configuration presents a significant advantage by effectively reducing the recombination of charge carriers at the interfaces of Z-scheme heterojunctions. The phase transition temperature of the WO 3-x nanoparticles was closely aligned with the exfoliation temperature of g-C 3 N 4 , which facilitated optimal interaction and resulted in a uniform dispersion of WO 3-x nanoparticles on the g-C₃N₄ nanosheets. Structural, elemental, and optical analyses verified the homogeneous incorporation of WO 3-x into g-C 3 N 4 . Electron microscopy FE-SEM revealed that WO 3-x nanoparticles were evenly distributed across the g-C 3 N 4 nanosheets, enhancing the photocatalytic activity compared to both pristine WO 3-x nanoparticles and g-C 3 N 4 nanosheets. The photocatalytic efficiency was assessed for the degradation of methylene blue (MB) under visible light and UV irradiation, with the g-C 3 N 4 /WO 3-x (90:10 wt ratio) nanocomposite demonstrating superior activity, achieving rate constants of 1.54 h⁻¹ for MB approximately 8.56 times greater than that of pure WO 3-x . Additionally, the Z-scheme charge carrier migration mechanism and visible light absorption convergence activity contributed to the accelerated degradation of organic dyes. This study also examined the photocatalytic reaction mechanism using several scavenger tests and also evaluated the reutilization properties of the photocatalysts, showcasing their excellent stability and efficiency over multiple cycles.