N3C-Defect-Tuned g-C3N4 Photocatalysts: Structural Optimization and Enhanced Tetracycline Degradation Performance

The introduction of nitrogen defects in graphitic carbon nitride (g-C3N4) has the important effect of improving its photocatalytic performance. This study employs a simple and environmentally friendly one-step pyrolysis method, successfully preparing g-C3N4 materials with adjustable N3C defect concentrations through the calcination of a urea and ammonium acetate mixture. By introducing N3C defects and adjusting the band structure, the conduction band of the g-C3N4 was shifted downward by 0.12 V, overcoming the traditional application limitations of N3C defects and enabling an innovative transition from enhanced oxidation to enhanced reduction capabilities. This transition significantly enhanced the adsorption and activation of O2. Characterization results showed that the introduction of N3C defects increased the specific surface area from 44.07 m2/g to 87.08 m2/g, enriching reactive sites, while narrowing the bandgap to 2.41 eV enhanced visible light absorption capacity. The g-C3N4 with N3C defects showed significantly enhanced photocatalytic activity, achieving peak performance of 54.8% for tetracycline (TC), approximately 1.5 times that of the original g-C3N4, with only a 5.4% (49.4%) decrease in photocatalytic efficiency after four cycles of testing. This study demonstrates that the introduction of N3C defects significantly enhances the photocatalytic performance of g-C3N4, expanding its potential applications in environmental remediation.