Anchoring single-atom Cu on tubular g-C3N4 with defect engineering for enhanced Fenton-like reactions to efficiently degrade carbamazepine: Performance and mechanism

Efficient construction of the active site is crucial for Fenton-like reactions. In this study, tubular carbon nitride with different vacancies (V-TCN) was prepared by simple temperature control. The affinity of the nitrogen atom generated by the carbon vacancy was used to anchor single-atom Cu, which achieved the precise regulation of Cu, reduced agglomeration, and maximally exposed the active site to enhance the activation of H2O2. Density functional theory calculations revealed that the single-atom Cu anchored in the C2 vacancy exhibited the lowest formation energy and the shortest Cu-N bonds. The results showed that Cu/V550-TCN had excellent degradation performance for the hard-to-degrade carbamazepine over a wide pH range (pH = 5–11), and singlet oxygen was the main active species during the degradation process. Additionally, the redox cycles of Cu(I)/Cu(II) and Cu(II)/Cu(III) accelerated the Fenton-like reaction. Five possible degradation pathways for carbamazepine were proposed based on liquid phase mass spectrometry analysis. This study provides a new insight into the role of surface defects in regulating the active site to promote the Fenton-like reaction for the degradation of stubborn pollutants.