A study on water dispersible graphitic carbon nitride photocatalyst for the removal of organic dyes

Abstract

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, thiourea by thermal treatment and different thermal polymerization atmosphere (air, carbon dioxide and nitrogen). The effects of g-C3N4 precursors and thermal polymerization atmosphere 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 and thermal polymerization atmosphere for bulk g-C3N4. The presence of foreign atoms (sulfur, S) in thiourea induced the formation of sulfur-containing nano porous water-dispersible g-C3N4. The highest MB adsorption ability and charge separation efficiency of the S-containing nano porous water-dispersible g-C3N4 prepare in N2 atmosphere photocatalyst exhibited a synergistic effect on MB photodegradation, resulting in the highest photocatalytic activity.