Manipulation of Oxygen Vacancies and Charge Transfer for Enhancing Visible–Near-Infrared Photodegradation

Photocatalytic degradation technology has drawn extensive attention due to its ability to utilize light energy for pollutant degradation. However, the generation of superoxide and hydroxyl radicals under broad-spectrum light confronts significant challenges. Herein, N-GQDs/TiO_2–x was rationally designed by adjusting oxygen vacancies (O_v) densities and constructing interfacial charge transfer channels. First, in situ XRD and EPR investigations disclosed that lowering the calcination temperature enabled the easy formation of rich oxygen vacancies. These vacancies introduced mid-gap states within the bandgap of TiO_2–x, thereby facilitating efficient light absorption. Meanwhile, the increased O_v density enhanced electron transport and facilitated electron escape in TiO_2–x. Moreover, an interfacial charge transfer channel was established between N-GQDs and TiO_2–x, which effectively promoted the transfer of photogenerated carriers. Because of these structural and electronic modifications, both ·OH and ·O₂^– could be readily generated under visible and near-infrared light irradiations. Notably, under the irradiation of 470 nm LEDs, 99.3% of acid chrome blue K (AcbK) was degraded by N-GQDs/TiO_2–x within 120 min. This work emphasizes the vital synergistic role of oxygen vacancies and interfacial charge-transfer channels, guiding the design of high-performance, full-spectrum photocatalysts for environmental applications.