Synthesis and Visible-Light Photocatalytic Activity of Graphite-like Carbon Nitride Nanopowders

Graphite-like carbon nitride (g-C3N4) nanopowders were synthesized by heat treatment of urea in air at a temperature of 450–550°С for 30 min and studied by X-ray diffraction and infrared spectroscopy. The main processes resulting in the formation of g-C3N4 from urea under the above conditions was established using the method of simultaneous thermal analysis. It was found that with an increase in the processing temperature of urea from 450 to 550°C, a rise in the specific surface of the powders occurs from 43.3 to 58.6 m2 g–1, as well as an increase in the crystallite sizes of graphite-like carbon nitride in the crystallographic direction (002) from 2.8 to 4.1 nm. According to the results of scanning electron microscopy and low-temperature nitrogen adsorption, the obtained graphite-like carbon nitride powders have a mesoporous structure and are characterized by an average pore size of 6.6–13.8 nm and porosity of 0.07–0.20 cm3 g–1. According to the results of diffuse reflectance spectroscopy, it was found that g-C3N4 nanopowders absorb radiation in the visible region and have a band gap of 2.9 eV. The photocatalytic activity of the obtained graphite-like carbon nitride during the oxidation of an aqueous murexide solution under the influence of visible light was analyzed and it was shown that the obtained g-C3N4 nanopowders have activity close to that of the commercial TiO2 photocatalyst (AEROXIDE P25). In view of the high activity and low cost, the obtained powders of graphite-like carbon nitride can be used as the substrate for new photocatalytic materials.