Facile synthesis of nitrogen vacancy-enriched polymeric carbon nitride via the trace manganese-induced precursor recrystallization process for photocatalytic degradation

A nitrogen vacancy-enriched polymeric carbon nitride (MNCN-1) is successfully prepared by one-step thermal polymerization of 3-amino-1,2,4-triazole crystals obtained by the recrystallization process induced via trace manganese species in this study. With a small amount, natural pH and anionic coexist conditions, MNCN-1 shows excellent performance in photocatalytic degradation of RhB, and it also shows good removal of antibiotic contaminants. Several analytical techniques results illustrate that the induction of trace manganese species facilitates the formation of nitrogen vacancies, and the nitrogen vacancies play a significant role in optimizing band structure and inhibiting the recombination of photo-generated carriers. MNCN-1 owns the maximum abundance of nitrogen vacancies. The increased N-vacancies cause a negative shift of the conduction potential, thus enhancing the thermodynamic driving forces and the kinetic of active radical generation. The much stronger reduction capability, increased involvement of trapped electrons in the ORR reaction and more abundant reaction centers for O2 molecules make the N-vacancy-enriched MNCN-1 achieve enhanced radicals' generation through a two-step single-electron reduction reaction (O2 -> center dot O2- -> H2O2). This study expands the strategy of constructing nitrogen-rich vacancies in polymeric carbon nitride, and elucidates the mechanism of its defective structure in enhancing the photocatalytic activity of PCN.