Magnetic field-enhanced spin polarization in Fe-doped CdS for photocatalytic superoxide generation and Microcystis aeruginosa removal.

Photocatalytic algae inactivation has emerged as a widely adopted strategy for water treatment, yet its efficiency remains limited by rapid recombination of photogenerated electrons and insufficient reactive oxygen species (ROS) generation in conventional semiconductors. To address these challenges, we developed a spin-polarized dilute magnetic semiconductor by doping Fe into CdS (Fe-CdS), Fe deposition extended the light absorption range and reduced the recombination of photogenerated carriers compared to pristine CdS, which accelerates the algal inactivation rate by 14.25-fold. Furthermore, under an external magnetic field, the spin regulation effect significantly increases photogenerated charge separation and promotes surface ROS production. Photocatalytic algae inactivation rate by Fe-CdS with magnetic field could be increased by 2.5 times than that without magnet filed. This work not only demonstrates a novel magnetic ion doping approach to engineer spin-active photocatalysts but also establishes magnetic field regulation as a universal strategy to amplify algal removal performance.