Defects and polarization charge cooperatively optimized Z-scheme NVs-g-C3N4/Bi/BiO1-xI heterojunction for full-spectrum catalytic organic pollutants mineralization and NO deep oxidation

Abstract

The application of photocatalysis technology still remains formidable challenges due to the limitations in the utilization of solar energy, the separation efficiency and redox ability of photogenerated charge carriers. In this work, we construct a Z-scheme NVs-g-C₃N₄/Bi/BiO_1-xI heterojunction through a HNO₃-assisted in-situ solvothermal method. Satisfactorily, full-spectrum light absorption is achieved by co-modifying by defects (nitrogen vacancies, oxygen vacancies and disorder micropores) and plasma Bi. Additionally, the band structures of NVs-g-C₃N₄ and Bi/BiO_1-xI are up-shifted and down-shifted, respectively, through interface polarization induced charge transfer modulation, further improving the oxidation-reduction capacities of electron-hole pairs. Meanwhile, owing to the charge capture and transport effects of intraband defect states and interface heterojunction, combined with the localized electromagnetic field enhancement induced by defects and plasma Bi, the charge separation efficiency is remarkably improved, and carrier lifetime is prolonged. Hence, the prepared NVs-g-C₃N₄/Bi/BiO_1-xI heterojunction exhibits boosted photocatalytic activity. Under visible and NIR light irradiation, the highest degradation rates of tetracycline can reach 0.0527 min^-1 and 0.0113 min^-1, respectively, which are 4.50 (2.64) and 5.14 (3.42) times higher than those of NVs-g-C₃N₄ (Bi/BiO_1-xI). Furthermore, upon illumination of visible light, 71.30% of NO can be removed by the optimal heterojunction, and the generation of toxic NO₂ is significantly suppressed. This work reveals the synergistic mechanism between defects, metal plasma and Z-scheme heterostructure in the photocatalytic processes, and provides a novel strategy for the rational design and construction of photocatalytic materials for solar energy-driven environmental cleaning.