Mechanochemically synthesized MnO2-gCN nanocomposite for photocatalytic dye and phenol degradation: A combined experiment and DFT study

Abstract

We present the large-scale synthesis of Manganese dioxide-graphitic carbon nitride (MnO2-gCN) nanocomposite using a mechanochemical process. Hydrothermally synthesized rod-shaped MnO2, combined with pyrolyzed gCN powder in appropriate proportions was mechanically ball-milled to form the MnO2-gCN composite structure. The resulting nanocomposite characterized through X-ray diffraction, Fourier transformed infrared spectroscopy, scanning electron microscopy, UV–Vis spectroscopy, and photoluminesce study revealed the successful anchoring of gCN with MnO2 nanostructure. Subsequently, the photocatalytic activity of MnO2-gCN nanocomposite was assessed by studying the degradation of Rhodamine B, Eosin B, Congo red, Methylene Blue dyes and toxic phenol pollutants under UV light exposure. The MnO2-gCN hybrid catalyst demonstrated impressive degradation efficiency, ca. 90% for Rhodamine B dye and 70% for phenol in 3 h and remarkable stability upto three cyclic runs. The superior performance of the composite, in comparison to its individual counterparts (MnO2 or gCN), can be attributed to the effective separation of photogenerated electron-hole (e−−h+) pairs and the suppression of charge recombination at the interface. First principle based density functional theory calculations also support the experimental findings and the conclusion of this study.

Keywords

• MnO2/gCN nanocomposite
• Ball-milling
• Photocatalysis
• Dye degradation
• Phenol degradation
• Density functional theory