Gamma Irradiation-Engineered g-C3N4 Nanosheets via Electrochemical Exfoliation for Enhanced Photocatalytic Degradation of Methylene Blue

Graphitic carbon nitride (g-C3N4) has attracted sustained interest as a visible-light-driven photocatalyst; however, its practical efficiency is often constrained by limited surface accessibility and rapid recombination of photogenerated charge carriers. Herein, g-C3N4 nanosheets were prepared via an environmentally benign electrochemical exfoliation route and subsequently modified through controlled gamma irradiation (γ-irradiation) in the dose range of 0–50 kGy. Structural analysis revealed that the crystalline framework of g-C3N4 remained preserved after irradiation, while the average crystallite size decreased from ~24.6 to ~18.4 nm, accompanied by an increase in lattice microstrain from 2.05 × 10-3 to 2.68 × 10-3. Optical characterization demonstrated dose-dependent tuning of the band structure, with direct band gap energies shifting from ~3.0 to ~3.2 eV and indirect transition energies ranging from ~2.4 to ~2.7 eV. Photoluminescence (PL) and time-resolved measurements indicated a pronounced suppression of non-radiative recombination at moderate irradiation levels, with the carrier lifetime reaching a maximum of ~4.6 ns at ~25 kGy. In parallel, γ-irradiation induced a measurable enhancement in surface area and pore characteristics. These combined effects resulted in a marked improvement in visible-light photocatalytic degradation of methylene blue (MB), following pseudo-first-order kinetics. The results demonstrate that γ-irradiation provides an effective and contamination-free means of optimizing the structural and photophysical properties of g-C3N4 nanosheets for photocatalytic applications.