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

In this research, g-C₃N₄/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-C₃N₄ 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-C₃N₄, 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-C₃N₄. Electron microscopy FE-SEM revealed that WO_3-x nanoparticles were evenly distributed across the g-C₃N₄ nanosheets, enhancing the photocatalytic activity compared to both pristine WO_3-x nanoparticles and g-C₃N₄ nanosheets. The photocatalytic efficiency was assessed for the degradation of methylene blue (MB) under visible light and UV irradiation, with the g-C₃N₄/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.