Construction of a direct Z-scheme Zn3V2O8/g-C3N4 heterojunction for highly efficient photocatalytic degradation of Rhodamine B

To overcome rapid charge recombination, a direct Z -scheme Zn 3 V 2 O 8 /g-C 3 N 4 heterojunction was designed, thus boosting photocatalytic performance. A suite of composite photocatalysts, with meticulously tuned Zn 3 V 2 O 8 mass ratios (x = 40, 60, and 80 wt%), were synthesized via a facile hydrothermal route. Comprehensive characterization, including XRD, SEM, UV–Vis DRS, PL spectroscopy, and photo-electro-chemical measurements confirmed the formation of intimate interfacial contact between Zn 3 V 2 O 8 and g-C 3 N 4 . This tailored interfacial architecture effectively promotes visible-light absorption and facilitates the separation and transfer of photo-generated charge carriers. Notably, the Zn 3 V 2 O 8 (60 wt%)/g-C 3 N 4 composite achieved 91% degradation of RhB within 120 min under simulated solar irradiation, substantially outperforming pristine g-C 3 N 4 (57%). Radical trapping experiments and electron spin resonance (ESR) spectroscopy identified superoxide radicals ( O 2 − ) and holes (h + ) as the primary active species. Based on these findings, a direct Z -scheme charge transfer mechanism is proposed, wherein photoinduced electrons in the conduction band of Zn 3 V 2 O 8 recombine with holes in the valence band of g-C 3 N 4 . This synergistic recombination pathway preserves the most energetic electrons in g-C 3 N 4 and holes in Zn 3 V 2 O 8 , endowing the system with strong redox capacity for the simultaneous generation of O 2 − and OH radicals, which collaboratively drive the efficient degradation of RhB. This study provides a rational design framework for constructing high-performance g-C 3 N 4 -based Z -scheme photocatalytic systems.