Density Functional Theory Study on the Impact of External Magnetic Fields on the Photocatalytic Properties of Metal‐Doped Titanium Dioxide

Home-made pure TiO₂ , Fe/TiO2l₂, Co/TiO₂, Cr/TiO₂, Cu/TiO₂ and Mn/TiO₂ were tested for methylene blue degradation under UV light with a 0.1 T magnetic field (MF). Fe/TiO₂ showed the greatest improvement, with moderate effects for pure, Cu- and Mn-doped samples, while Co- and Cr-doping reduced degradation. Mechanisms were explored using DFT+U (PBE functional, VASP code) computation. DOS patterns indicates noticeable spin polarization as transition metals are doped into lattice and various degrees of bandgap decrease and the introduction of new bands within the bandgap region. The charge density patterns indicated that the doped transition metals can form new recombination centers to inhibit the electron and hole recombination. Optical properties simulations estimated photocatalytic performance through dielectric function, Cu/TiO₂ stands out with the highest dielectric constant, suggesting its superior potential for light absorption. According to the spin density results, Cu/TiO₂, Fe/TiO₂, and Mn/TiO₂ showed the highest potential of being affected by an external magnetic field, consistent with the experimental findings of enhanced photo degradation in the presence of an external MF. This research aims to elucidate the mechanisms of the external magnetic field effect on photocatalysis at the electron level.