Enhanced spin polarization in GQDs/TiO2 fibers via magnetic field and oxygen vacancies for photocatalysis

In this study, graphene quantum dots/titanium dioxide (GQDs/TiO₂) fiber membranes with engineered oxygen vacancies were fabricated using a combination of electrospinning and solvothermal techniques. Oxygen vacancies, as key active sites, enabled spin polarization during the photocatalytic reaction, and the material’s spin polarization was verified by X-ray Absorption Spectroscopy (XAS) and Density Functional Theory (DFT). For the first time, the effects of high magnetic fields (1000–5000 mT) on photocatalytic performance were systematically explored. The findings reveal that the magnetic field markedly enhances spin polarization, facilitating synergistic interactions between oxygen vacancies and photogenerated electrons while significantly suppressing carrier recombination. Under these conditions, the GQDs/TiO₂ fiber membranes achieved a remarkable 52.44% increase in the degradation rate of methylene blue compared to zero-field conditions. Additionally, the study introduces the concept of magnetic field-induced progressive energy level modulation, wherein defect state energy levels undergo gradual adjustment before stabilization under magnetic influence. This work provides critical insights into radical generation mechanisms driven by the interplay between magnetic fields and oxygen vacancies, offering a novel pathway for designing advanced photocatalysts with broad applications in water pollution treatment and sustainable energy solutions.