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

Highlights: • Water-dispersible graphitic carbon nitride is synthesized from different precursors. • All water-dispersible photocatalysts show the morphology of thin-layered structure. • Water-dispersible photocatalyst from thiourea (TCp) has S-and O-containing groups. • TCp photocatalyst shows highest adsorption capacity and lowest recombination rate. • TCp exhibits the best photocatalytic activity for methylene blue photodegradation. 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.