Comparison of the Effects of Brominated Perylenediimide and Perylene Tetraester Modified G-C₃N₄ S-Scheme Nanocomposites on the Photocatalytic Degradation of Anionic and Cationic Dyes and Herbicide

Metal-free g-C₃N₄ (graphitic carbon nitride) is a promising candidate for the next-generation visible light-responsive photocatalyst; however, the recombination and transfer of the photogenerated charge carriers restrict its photocatalytic performances. The exfoliated g-C₃N₄ sensitized with brominated perylenediimide (dBrPDI) and perylene tetraester (dBrPTE) enhances the photocatalytic performance due to improved charge separation, light absorption, charge transfer and, thereby, overall efficiency in pollutant degradation. The g-C₃N₄/dBrPTE hybrid composite exhibits the fastest photocatalytic degradation against rhodamine B (RhB) pollutants. The g-C₃N₄/dBrPTE hybrid composite degrades RhB with a 2.34-fold improvement over pure g-C₃N₄, while the g-C₃N₄/dBrPDI hybrid composite degrades with a 1.56-fold increase over pure g-C₃N₄. The g-C3N4/dBrPDI hybrid composite shows the highest photocatalytic efficiency against methyl orange (MO) pollutants. The g-C₃N₄/dBrPDI hybrid composite degrades MO with a 2.25-fold improvement over pure g-C₃N₄, while the g-C₃N₄/dBrPTE hybrid composite degrades with a 1.8-fold increase over pure g-C₃N₄. Unlike MO and RhB, the perylene dye sensitization does not enhance the photocatalytic degradation of 2,4-dichloro phenoxy acetic acid (2,4-D) and no sustained increase in efficiency is not observed. Overall, these results suggest that photocatalytic efficiency depends not only on the sensitized photocatalyst material but also on the interaction between the sensitized photocatalyst and the chemical and ionic properties of the pollutants in the aquatic media.