The photo-Fenton activity of graphitic carbon nitride (g-C3N4) has been widely studied, nevertheless, its Fenton-like catalytic behavior in the dark has not yet been demonstrated. In the present work, it is shown that oxygenated g-C3N4 obtained at different temperatures (500-600 °C) can degrade indigo carmine with hydrogen peroxide in the dark by a reaction similar to a conventional Fenton's reaction. Based on an extensive characterization of g-C3N4, we conclude that Fenton-like activity is directly related to the oxygenated functional groups on g-C3N4 structure, mainly by -OH functional groups. Oxygenated functional groups (e.g., hydroquinone-like groups) can reduce the H2O2 and generate oxidizing hydroxyl radicals, just like in the Fenton reaction performed by metals. In addition to new information on g-C3N4 surface reactivity revealed by this study, the metal-free oxygenated g-C3N4 catalyst may be an alternative to traditional metal catalysts used in Fenton-like reactions for advanced oxidation.
Keywords: Fenton-like reaction; Graphitic carbon nitride; Oxygenated functional groups.
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