In situ synthesis of g-CN/TiO heterojunction by a concentrated absorption process for efficient photocatalytic degradation of tetracycline hydrochloride.

The construction of heterojunctions between semiconductors is a preferred route to improve overall photocatalytic activity. In this work, a facile and feasible method was innovatively developed to one-step prepare g-CN/TiO heterojunctions via an absorption-calcination process using nitrogen and titanium precursors directly. This method can effectively avoid interfacial defects and establish a tight interfacial connection between g-CN and TiO. The resultant g-CN/TiO composites exhibited prominent photodegradation efficiency for tetracycline hydrochloride (TC-HCl) under visible light and simulated-sunlight irradiation. The optimal g-CN/TiO composite (urea content of 4 g) showed the highest photocatalytic efficiency, which can degrade 90.1% TC-HCl under simulated-sunlight irradiation within 30 min, achieving 3.9 and 2 times increases compared to pure g-CN and TiO, respectively. Besides, photodegradation pathways based on the role of active species ·O and ·OH were identified, indicating that a direct Z-scheme heterojunction was formed over the g-CN/TiO photocatalyst. The enhanced photocatalytic performance can be attributed to the close-knit interface contact and the formation of Z-scheme heterojunction between g-CN and TiO, which can accelerate the photo-induced charge carrier separation, broaden the spectra absorption range, and retain a higher redox potential. This one-step synthesis method may provide a new strategy for the construction of Z-scheme heterojunction photocatalysts consisting of g-CN and TiO for environmental remediation and solar energy utilization.