Efficient Photocatalytic H₂O₂ Production Ability of a Novel Graphitic Carbon Nitride/Carbon Composites under Visible Light

In the present work, using one-step calcination of a mixture made of potassium hydroxide (KOH), melamine, and microplastics, this work prepares a novel graphitic carbon nitride/carbon (g-C₃ N₄ /C) composite, which can be employed to photo-catalytically produce hydrogen peroxide (H₂ O₂ ) at a high rate up to 6.146 mmol g^-1 h^-1 under visible light irradiation. By analyzing the energy band structure of the catalyst, the production of H₂ O₂ in this system consists of two single-electron reactions. The modification of KOH makes abundant N-vacancies caused by cyano-groups in g-C₃ N₄ , enhancing the electron absorption ability. Moreover, the introduction of graphitic carbon increases its specific surface area and porosity and improves the adsorption ability of O₂ . Simultaneously, their synergism reduces the g-C₃ N₄ band gap, making both the conduction-band and valence-band positions more negative, showing enhanced reduction ability, lowering the energy barrier for oxygen reduction, and greatly improving the photogeneration performance of H₂ O₂ .