Engineering ZnO/g-C₃N₄ Heterostructures for Enhanced Photocatalytic Performance under Solar Irradiation

A nanocomposite photocatalyst of zinc oxide and graphitic carbon nitride (ZnO/g-C3N4) was successfully synthesized through a facile one-step calcination approach using urea, melamine, and zinc acetate as precursors. Characterization techniques, including XRD, FESEM, FTIR, UV-vis, PL, and BET, were employed to confirm the formation of a well-defined heterostructure with optimized physicochemical properties. The incorporation of g-C3N4 into the ZnO matrix resulted in significant structural modifications, including a reduction in crystallite size (from 50.4 to 19.8 nm), an increase in lattice strain (from 0.239–0.589%), and an elevation in defect concentrations, thereby enhancing photocatalytic activity. Photoluminescence (PL) analysis revealed the effective suppression of electron-hole recombination via the established S-scheme charge transfer mechanism. The nanocomposite demonstrated excellent photocatalytic performance, achieving 94.8% methylene blue (MB) degradation within 60 minutes under solar light irradiation, representing a 2.5- and 3.2-fold enhancement compared to pristine ZnO and g-C3N4, respectively. This enhanced photocatalytic activity is attributed to the synergistic effects of a narrowed bandgap, efficient charge separation, and an increased number of active surface sites. These findings highlight the ZnO/g-C₃N₄ nanocomposite as a promising and cost-effective solution for solar-driven wastewater treatment applications.