O-Regulated N-Terminal Achieves Efficient Photocatalysis through Electronegativity-Induced Band Engineering

Band engineering has garnered significant attention for its role in tailoring the band structures of g-C3N4, which is crucial for enhancing the light collection and conversion processes. In this paper, a novel visible-light-driven g-C3N4 was synthesized by a simple and efficient thermal polymerization method, and the morphology and bandgap were modulated by incorporating a high electronegativity oxygen element (O). Scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), etc., were applied to analyze the morphology and chemical structure of the samples and the photogenerated charges separation performance was also investigated by ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), electrochemical impedance spectroscopy (EIS), etc. Besides, tetracycline (TC) photodegradation efficiency was tested, and the results show that the reaction rate constant and removal rate of MG0.002 are 0.0933 min–1 and 81.6% (within 60 min), and the recyclability and adaptability are excellent. Moreover, the mechanism of O regulatory was studied by element analyzer (EA) and X-ray photoelectron spectroscopy (XPS), and the results indicate that sp2-hybridized N atoms are preferentially replaced by O atoms in the MG0.02 structure. Finally, the TC degradation enhancement mechanism was investigated and the results indicated that the electrons were redistributed due to the influence of high electronegativity oxygen, which can not only generate midgap states and promote the visible light absorption, but also realize the effective transfer and separation of photogenerated carriers, thus significantly improving the photocatalytic activity.