Hollow tubular graphitic carbon nitride catalyst with adjustable nitrogen vacancy: Enhanced optical absorption and carrier separation for improving photocatalytic activity

A hollow tubular graphitic carbon nitride (g-C3N4) with nitrogen vacancy was successfully prepared via simple hydrothermal calcination method. The hollow tubular structure has the functions of increasing the specific surface area, promoting the multiple scattering effect of light, as well as imparting the directional transfer of electrons. Simultaneously, the introduction of vacancy defect can manipulate the electronic structure of g-C3N4 with narrow band-gap and excellent charge carrier behavior. The catalytic activity of the photocatalysts were evaluated by the degradation reaction of chlortetracycline hydrochloride (CTC·HCl) and hydrogen evolution reaction (HER). The results indicated that the photocatalytic property of the resulting g-C3N4 tube with appropriate nitrogen vacancy was significantly better than that of original g-C3N4. Under visible light irradiation, ND-TCN-10 demonstrated the optimal photocatalytic degradation effect and achieved a hydrogen generation rate of 235.68 μmol g−1 h−1. In addition, based on the liquid chromatography-mass spectrometry (LC-MS), the main by-products of CTC·HCl and the possible degradation pathways were analyzed. The method of introducing nitrogen deficiency into the tubular structure provides a promising strategy for increasing the photocatalytic activity of g-C3N4-based materials.