Heterogeneous Fenton-like surface properties of oxygenated graphitic carbon nitride

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.