Defect Engineering in g-C3N4 Quantum-Dot-Modified TiO2 Nanofiber: Uncovering Novel Mechanisms for the Degradation of Tetracycline in Coexistence with Cu2+

Herein, g-C3N4 quantum-dot-modified TiO2 nanofibers were fabricated and used as an efficient photocatalyst for the investigation of the influence of Cu2+ and the interaction mechanism between Cu2+ and surface defects in tetracycline degradation. Results showed that the effect of Cu2+ switched from promoting to inhibiting the tetracycline degradation as the amount of Cu2+ accumulated on the catalyst surface increased. The introduction of surface defects can prevent the inhibiting effect of Cu2+, resulting in the more complete degradation of tetracycline in contrast to the non-defective sample. Theoretical calculations further revealed that the defects can be used to tune the conduction band of the composite, inducing the reduction reaction of Cu2+ and inhibiting the accumulation of Cu on the surface of catalysts. Moreover, the Cu introduced to the catalyst surface provided new active sites, thereby promoting photocatalytic degradation. These findings provide new insights into the design of advanced fiber materials for water purification in complex environments. [GRAPHICS] .