Synthesis of g-C₃N₄/ZnO composites with enhanced photocatalytic activity under visible light

The g-C₃N-4/ZnO composites were synthesized by heating a mixture of urea and ZnO at 500 ℃ and denoted as g-C₃N₄/ZnO-w, where w is the weight ratio of urea/ZnO and equals to 3, 4 and 5. The obtained materials were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy. The results showed that all g-C₃N₄/ZnO-w samples are composites of orthorhombic ZnO and g-C₃N₄. The photocatalytic activity of g-C₃N₄/ZnO-w samples was evaluated by degradation of methylene blue in water under visible light. Among them, g-C₃N₄/ZnO-4 sample exhibits the highest photocatalytic efficiency. The enhancement of photocatalytic activity of the g-C₃N₄/ZnO composites compared to single components, g-C₃N₄ and ZnO was observed, which can be attributed to the reduction of combination rate of photogenerated electron – hole pairs in the composites. (author)