Synergistic role of nitrogen vacancies and crystallinity in the efficient photo-oxidation of NO by graphitic carbon nitride

Visible light-driven photo-oxidation reactions hold significant potential for the treatment of gaseous pollutants. However, the weak internal electric field of carbon nitride (g-C 3 N 4 ) leads to sluggish migration of photogenerated carriers, while inefficient electron-hole pair separation further limits the overall photo-oxidation efficiency. In this study, nitrogen-vacancy (Nv) rich crystalline (Cs)/amorphous g-C 3 N 4 was synthesized using a two-step calcination method. The increased crystallinity facilitates faster carrier migration, broadens the potential difference between the crystalline and amorphous regions, and enhances the piezoelectric response. On the other hand, the incorporation of nitrogen vacancies (Nv) introduces asymmetry, generating a dipole field that significantly improves the efficiency of electron-hole pair separation. Moreover, the presence of NV improves the adsorption and activation of O 2 molecules, promoting the photo-oxidation of adsorbed NO via the generation of single linear oxygen ( 1 O 2 ). The resulting material, Cs-Nv-630, demonstrated excellent oxidative NO removal efficiency, achieving a removal rate of 95.3 % under visible light irradiation. This study highlights a novel strategy for enhancing photo-oxidation activity through structural engineering, leveraging crystallinity and dipole fields to optimize carrier migration and complexation.