One-step fabrication of nitrogen-deficient carbon nitride through pyrolysis of melamine and 1,2,4-triazole for its enhanced photocatalytic degradation

The construction of defects in semiconductor photocatalysts, as a kind of modification methods, plays an indispensable role in the enhancement of the photocatalytic performance. Herein, nitrogen defects were successfully introduced into the framework of graphite carbon nitride (CN-Tx) through thermal polymerization with melamine and 1,2,4-triazole as precursors. The existence of nitrogen defects in CN-Tx were confirmed to be located at the two-coordinated (N2c) CN–C lattice sites, which resulted in the destruction of its planar structure and the initiation of n-π∗ electron transition that greatly expanded the response range to visible light and improved the separation efficiency of photogenerated charge carrier. More significantly, CN-Tx could enhance photocatalytic water purification activity towards different kinds of pollutants. The photocatalytic rates of CN-T3 were estimated to be 2.54 (tetracycline) and 2.31 (2-hydroxynaphthalene) times higher than those of pristine g-C3N4. Furthermore, the possible photocatalytic degradation mechanism over CN-Tx photocatalyst was proposed by free radical trapping experiments combined with ERS characterization. This work provides an in-depth understanding of the important role of nitrogen defects in the electronic structure and chemical properties of g-C3N4 and its photocatalytic water purification performance.