Precursor-dependent fabrication of exfoliated graphitic carbon nitride (gCN) for enhanced photocatalytic and antimicrobial activity under visible light irradiation

In this work, we report the effective fabrication of exfoliated graphitic carbon nitride (gCN) photocatalysts through thermal exfoliation utilizing melamine, urea, and a combination of the two as precursors. As fabricated photocatalysts were characterized by different analytical techniques like XRD, FT-IR, UV-DRS, BET, FE-SEM HRTEM and XPS. Combining the various findings, it found that the gCN synthesized from urea has a loose nanosheet-like structure with smaller lamellae and a high surface area with porosity. The specific surface area for U-gCN was observed to be 168.98 m² g⁻¹, which was nearly 10 times higher than that of M-gCN (≈14.56 m² g⁻¹). Band gap energies using Tauc plot were estimated to be 2.57 eV for M-gCN, 2.68 eV for UM-gCN, and 2.82 eV for U-gCN, difference in the band gap energies was due to the peak shift observed in UV-DRS spectra. It was observed that thermally exfoliated U-gCN nanosheets were observed to be 5 times more efficient (98.4% degradation in 60 min) than M-gCN and UM-gCN in the photo-degradation of Methylene blue (MB) dye. Similarly, U-gCN photocatalyst showed remarkable ability to degrade tetracycline (TC) drug and the results exhibited that the TC antibiotic was almost completely degraded within 60 min of light exposure, at a rate of 0.0065 min⁻¹. Scavenger studies were also carried out to investigate the reactive species. Further the plausible degradation mechanism was studied by combining the results of Tauc plot and VB-XPS. Additionally, photocatalytic antibacterial experiments revealed that U-gCN have remarkable antibacterial activity against S. aureus bacteria. Overall, enormous thin sheet-like arrangement, porous structure (which leads to effective charge separation), high surface area and extended light absorption characteristics are all contributing factors for the remarkable photocatalytic efficiency of U-gCN.