Synthesis of large surface area C3N4 nanosheets by the soluble salt-assisted route, and their good photocatalytic degradation of dye

Carbon nitride is a good inorganic non-metallic material, and is widely used in the photocatalysis. However, its photocatalytic performance is significantly related to its morphological characteristics, especially its nanosheet-like morphology has recently attracted keen interest. In this paper, a soluble salt-assisted route is adopted. By ball milling melamine and Na₂SO₄ powder, the precursor can be evenly distributed over the surface of Na₂SO₄ particulates. Then through the thermal decomposition reaction, and finally by washing Na₂SO₄ with water, a large amount of carbon nitride nanosheet powders can be obtained. After the examinations by XRD, SEM, XPS, PL, and BET, the results show that the product has a hexagonal phase C₃N₄ structure, sheet-like morphology with two-dimensional sizes of several micrometers and a thickness of ten nanometers, a large surface area of 23.89 m²/g and a low PL intensity centered at 450 nm when compared with the bulk C₃N₄ powders, well known for enhancing its photocatalytic efficiency. According to expectation, the dye photocatalytic degradation rate over the C₃N₄ nanosheets is 90% in 30 min, but only 60% in the same time on bulk C₃N₄. Moreover the photocatalytic degradation reactions follow pseudo-first-order reaction kinetics, and the former rate constant is more than twice that the latter.

Graphical abstract

By ball milling melamine and sodium sulfate powder, the precursor can be evenly distributed over Na₂SO₄. Then through the thermal decomposition reaction, and finally by washing sodium sulfate with water, the pure carbon nitride nanosheets can be obtained