Temperature-controlled morphology evolution of graphitic carbon nitride nanostructures and their photocatalytic activities under visible light

Abstract

A series of g-C₃N₄ photocatalysts were synthesized by changing the temperature through air-assisted thermal polymerization and etching. The detailed characterization and analysis clearly revealed that the texture, surface structure, optical properties, and band structure of g-C₃N₄ depend on the preparation conditions such as atmosphere and temperature. The morphology of samples obtained at different temperatures undergoes sequential evolution from bulk to nanosheet with multilayer, nanosheet with few layer, moderately rolled nanosheet, tailored nanotube, nanoflakelet and even nanoparticles. Accordingly, the BET surface area increased dramatically from 4.5 m² g⁻¹ of bulk g-C₃N₄ to 210.1 m² g⁻¹ of modified sample obtained at 540 °C. The different textural and structural properties resulted in the different optical and electronic features. The exfoliated and tailored samples obtained by this method presented better photocatalytic performance as compared with bulk g-C₃N₄. Factors affecting the photocatalytic activity of g-C₃N₄ were discussed in details on the basis of the textural and structural characterization as well as the photocatalytic activity results. We found that the surface area, surface defects, and light absorption have great impacts on the photocatalytic activities of g-C₃N₄.