The effect of graphitic carbon nitride precursors on the photocatalytic dye degradation of water-dispersible graphitic carbon nitride photocatalysts

In this study, water-dispersible graphitic carbon nitride (g-C3N4) was synthesized through chemical oxidation of bulk g-C3N4 produced from different starting nitrogen-rich organic precursors such as dicyandiamide, melamine, urea, and thiourea by thermal treatment. The effects of g-C3N4 precursors on water-dispersible g-C3N4 photocatalysts were investigated using several characterization tools and photocatalytic degradation of methylene blue (MB). Exfoliation of bulk g-C3N4 by chemical oxidation gave rise to the characteristic properties of water-dispersible g-C3N4 such as a high surface area, thin-layered morphology, an increase in band gap, and significant reduction in the recombination rate of photogenerated electron-hole pairs, which improved the photocatalytic activity of water-dispersible g-C3N4 for MB photodegradation. The photocatalytic activities of water-dispersible g-C3N4 photocatalysts were also strongly influenced by N-rich g-C3N4 precursors for bulk g-C3N4. The presence of foreign atoms (sulfur, S) in thiourea induced the formation of sulfur-containing nanoporous water-dispersible g-C3N4. The highest MB adsorption ability and charge separation efficiency of the S-containing nanoporous water-dispersible g-C3N4 photocatalyst exhibited a synergistic effect on MB photodegradation, resulting in the highest photocatalytic activity.