Mie resonance-enhanced self-sensitized photocatalysis: pure TiO2 hollow nanospheres for high-efficient visible-light degradation of Rhodamine B

Dye sensitization has emerged as a promising strategy to enhance the visible-light photocatalytic performance of TiO 2 . However, conventional dye-sensitized photocatalytic systems face significant challenges, such as limited light absorption efficiency and secondary pollution caused by dye desorption and degradation. Herein, pure TiO 2 hollow nanospheres are prepared, and their size is regulated to excite Mie resonance, thereby enhancing the self-sensitized photocatalytic degradation of Rhodamine B (RhB) under visible light without the need for external sensitizers. By optimizing the diameter of the TiO 2 hollow nanospheres to approximately 370 nm (D370), we achieve a strong overlap between the Mie resonance wavelength and the absorption band of RhB. Under visible-light irradiation, D370 exhibits exceptional photocatalytic performance, achieving 94.3% degradation of RhB within 60 min and a reaction rate constant of 46.91×10 -3 min -1 , which significantly outperforms conventional TiO 2 nanoparticles. Using finite element method (FEM) simulations and multipole decomposition method, we reveal that the enhanced performance is driven by size-dependent Mie resonances, predominantly magnetic quadrupole resonances. These resonances localize and amplify the incident light field on and around the spherical shells, leading to a more than 4-fold enhancement in the electric field intensity and a substantial increase in RhB absorption. This work demonstrates the remarkable potential of pure TiO 2 materials for visible-light-induced photocatalytic degradation, achieving high efficiency without additional modification. Furthermore, it highlights the critical role of Mie resonance, particularly magnetic multipole contributions, in enhancing light utilization efficiency. These findings not only advance our understanding of light-matter interactions in photocatalytic systems but also provide a novel framework for designing high-performance photocatalysts, paving the way for broader applications in solar energy conversion and environmental remediation.