Efficient photocatalytic degradation of textile dye pollutants using thermally exfoliated graphitic carbon nitride (TE–g–C3N4)

Abstract

Graphitic carbon nitride (g–C₃N₄), an organic photocatalyst was reported to have beneficial properties to be used in wastewater treatment applications. However, g–C₃N₄, in its bulk form was found to have poor photocatalytic degradation efficiency due to its inherent limitations such as poor specific surface area and fast electron–hole pair recombination rate. In this study, we have tuned the physiochemical properties of bulk g–C₃N₄ by direct thermal exfoliation (TE–g–C₃N₄) and examined their photocatalytic degradation efficiency against abundant textile dyes such as methylene blue (MB), methyl orange (MO), and rhodamine B (RhB). The degradation efficiencies for MB, MO, and RhB dyes are 92 ± 0.18%, 93 ± 0.31%, and 95 ± 0.4% respectively in 60 min of UV light irradiation. The degradation efficiency increased with an increase in the exfoliation temperature. The prepared catalysts were characterized using FTIR, XRD, FE-SEM, EDAX, BET, and UV-DRS. In BET analysis, TE–g–C₃N₄ samples showed improved surface area (48.20 m²/g) when compared to the bulk g–C₃N₄ (5.03 m²/g). Further, the TE–g–C₃N₄ had 2.98 times higher adsorption efficiency than the bulk ones. The free radicals scavenging studies revealed that the superoxide radicals played an important role in the photodegradation for dyes, when compared to the hydroxyl radical (^.OH) and the photo-induced holes (h⁺), Photoluminescence (PL) emission and electrochemical impedance spectroscopy (EIS) spectra of TE–g–C₃N₄ indicated a lowered electron–hole pairs’ recombination rate and an increased photo-induced charge transfer respectively. Further, the TE–g–C₃N₄ were found to have excellent stability for up to 5 cycles with only a minor decrease in the activity from 92% to 86.2%. These findings proved that TE–g–C₃N₄ was an excellent photocatalyst for the removal and degradation of textile dyes from wastewater.