Surface-engineered anisotropic g-C3N4 photocatalysts via green-exfoliation for visible light-driven water remediation

This study explores the modification of g-C3N4 (GCN) using extracts of betel (Piper betle) leaves and veld-grape (Cissus quadrangularis) stems. The obtained results indicate that these green extracts can effectively exfoliate the GCN-layers, modifying both the 2D structure and the 3D morphological features of GCN, leading to simultaneous chemical and physical modifications in the system. The FESEM and HRTEM images revealed the exfoliated layers with a spike-like morphology for betel extract-treated GCN (B-GCN) system, while a porous nature, along with curled layer structure, is observed in the veld extract-treated GCN (V-GCN) system. An extended absorption in visible-light region along with a reduced band gap energy is observed for V-GCN (-2.22 eV) and B-GCN (-2.29 eV), compared to pristine GCN (-2.41 eV). These improvements attributed to the anisotropic morphology -induced alterations in the band structure of the systems. A notable carrier recombination resistance is also realized from the PL spectra of the treated-GCNs. The visible light-driven photocatalytic efficiencies of both the pristine and treated-GCNs in degrading methylene blue (MB), rhodamine B (RhB) and their mixture (MB+RhB) are investigated under solar irradiation. The results revealed that the V-GCN and B-GCN exhibited around 100% and over 80% degradation for MB and RhB dye, respectively. Notably, in the case of mixed dyes, the treated-GCN systems demonstrated enhanced degradation compared to pristine. This enhancement can be attributed to their improved band structure resulting from a greater layer exfoliation, morphological changes, and the presence of nitrogen defects in the modified systems. The recycling studies demonstrated that the extract-treated GCN is sable and can remain sustainable for scaled-up photocatalytic applications.