On P-doping of graphitic carbon nitride with hexachlorotriphosphazene as a source of phosphorus

The synthesis of P-doped graphitic carbon nitride (PCN) by in situ doping via co-pyrolysis of melamine and hexachlorocyclotriphosphazene (HCCP) is being investigated. The amount of HCCP varies between 2 and 40 wt% and the results show continuous enrichment of graphitic carbon nitride (CN) by phosphorus. The detailed characterization of prepared samples leads to the proposition of the occurrence of phosphorus in synthesized samples as well as to the proposition of a P-doping mechanism. The results of the characterization techniques used indicate that with up to 1.2 wt% of phosphorus in final PCN, phosphorus predominantly substitutes carbon in the structure. An increase of the phosphorus content to 2.44 wt% causes its incorporation into substitutional positions and part of the phosphorus occurs in other forms. PCN with 2.44 wt% of phosphorus obtained from the mixture of melamine with 20 wt% of HCCP thermally treated at 525 °C shows the highest photodegradation activity under VIS irradiation.