The role of the g-C3N4 precursor on the P doping using HCCP as a source of phosphorus
Vlastimil Matějka, Radim Škuta, Kryštof Foniok, Vlastimil Novák, Daniel Cvejn, Alexandr Martaus, Monika Michalska, Jiří Pavlovský, Petr Praus
Abstract
This work describes the doping of graphitic carbon nitride (g-C3N4) with phosphorus performed by 2-h heat treatment of a mechanical mixture of g-C3N4 precursor (urea, dicyandiamide, and guanidine hydrochloride) with hexachlorocyclotriphosphazene at 525 °C. The amount of fixed phosphorus in the resulting g-C3N4 structure reached approximately 10 wt% in the case of the urea precursor. For the other two precursors, the fixed phosphorus content in the final products was less than 5 wt%. Several experimental techniques (SEM, XRFS, TG, XRD, FTIR, physisorption of nitrogen, UV-VIS DRS, PL spectroscopy, and electrochemical analysis) were used to characterize the prepared samples. The photodegradation activity of the samples was determined by degradation of Rhodamine B under irradiation with visible light (420 nm). In general, the photodegradation activity of the samples was dependent on the phosphorus content. The highest photodegradation activity was obtained for urea-based g-C3N4 doped with the lowest phosphorus content, with a threefold increase in calcination product yield. The mechanism of incorporation of phosphorus into the final g-C3N4 structure was explained as a two-phase process.