M. Saffioti, F. Sordello, C. Paganini, F. Cristaudo, M. Ginepro, T. Ohno, D. Fabbri, P. Calza
This study investigates the effects of phosphorus (P) doping onto the structural, optical, and photocatalytic properties of graphitic carbon nitride (g-C 3 N 4 ). g-C 3 N 4 materials doped with different amounts of P were synthesized to identify the optimal phosphorus loading for enhancing photocatalytic degradation of carbamazepine (CBZ), a highly persistent contaminant, while simultaneously improving hydrogen peroxide production. Structural and morphological analyses showed that all materials preserved the g-C 3 N 4 structure, although crystallinity decreased with increasing P content. More defined melem-related characteristics and better structural order were present at low and moderate doping levels (5–17.5 mmol), whereas no significant morphological differences were observed. The band gap increased slightly at high phosphorus loadings (>30 mmol), suggesting modifications of electronic transitions induced by a massive dopant presence. These changes affected photocatalytic behaviour: CBZ degradation was slow under visible light, but greatly enhanced under UV-A irradiation, with P(5)C 3 N 4 showing the highest activity. Higher phosphorus loadings led to reduced performance, consistent with reduced crystallinity and melem species. H 2 O 2 production increased with phosphorus content and was further promoted in the presence of CBZ, acting as a sacrificial agent. A general inverse relationship emerged between maximum H 2 O 2 levels and CBZ degradation efficiency, except for P(5)C 3 N 4 , which retained the best performance in both processes. To further elucidate the photocatalytic mechanisms, ten transformation products were identified including mono- and di-hydroxylated derivatives and acridinic species. Finally, P(5)C 3 N 4 maintained good CBZ removal efficiency in two actual water matrices, wastewater effluent and aquaculture water, so proving material’s applicability under environmentally relevant conditions.