The role of the g-C3N4 precursor on the P doping using HCCP as a source of phosphorus

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.