Enhanced degradation ability of heterojunction via construction of typical morphologies of carbon nitride: Mechanistic insights and theory calculations

Carbon nitride (C₃N₄)-based heterojunctions have demonstrated remarkable potential in suppressing photogenerated carrier recombination and enhancing light-energy conversion efficiency, making them promising candidates for photocatalytic applications. However, the synergistic interplay between morphology regulation and heterojunction engineering remains underexplored. In this study, three distinct C₃N₄ nanostructures—bulk (BCN), spherical (SCN), and vein-network (LCN)—were successfully synthesized via high-temperature calcination and solvothermal methods using melamine as the precursor. Subsequently, a Z-scheme C₃N₄/WO₃ heterojunction was constructed and employed for visible-light-driven tetracycline (TC) degradation. Comprehensive experimental characterizations and theoretical calculations revealed that morphological optimization critically influences the crystal structure, band alignment, and photoelectrochemical properties of C₃N₄. Finite-difference time-domain (FDTD) simulations and photoelectrochemical analyses further elucidated the mechanistic role of nanostructure design in enhancing charge separation and photoconversion efficiency. The Z-scheme heterojunction not only promoted localized charge density distribution but also significantly improved light absorption and carrier separation, leading to superior TC degradation performance. Notably, the LCN/WO₃ composite achieved 96.5 % TC removal within 60 min, outperforming BCN/WO₃ (75.3 %) and exhibiting degradation rates 2.24 and 8.48 times higher than those of BCN and pristine WO₃, respectively. This work highlights the synergistic benefits of morphology control and heterojunction engineering in optimizing C₃N₄-based photocatalysts, offering a viable strategy for efficient antibiotic degradation.