Schottky junction-rectified spin polarization as a "fail-safe" charge management strategy for efficient ceftiofur removal and real pharmaceutical wastewater remediation.

Suppressing charge recombination is essential for efficient photocatalytic pollutant removal. Spin polarization drives carrier spins into a parallel configuration, rendering singlet recombination spin forbidden, yet carriers with antiparallel spins remain active for recombination. To tackle this issue, a "fail-safe" approach for charge regulation was developed by integrating inherent spin polarization with Schottky interface formation within Co-modified MgIn2S4/Mo2C heterostructure. The substitutional Co2+ ions create a spin-polarized lattice that suppresses the spin-allowed singlet recombination pathway, while the Mo2C component forms a one-way Schottky barrier that extracts the residual antiparallel-spin electrons before they can recombine. Under visible light and an external magnetic field, this complementary architecture delivered a ceftiofur degradation efficiency of 97.9% within 60 min and performed remarkably in real pharmaceutical wastewater treatment, reducing the chemical oxygen demand (COD) from 8261 mg/L to 1966 mg/L. The decomposition pathway of ceftiofur was further elucidated by mass spectrometry and density functional theory (DFT) calculations, and the toxicity of the resulting intermediates was evaluated through computational toxicology. In-depth spectroscopic investigations together with theoretical simulations revealed that the spin-polarized environment originates from the high-spin 3d7 electronic configuration of substitutional Co2+, and that its synergy with the Schottky junction effectively rectifies charge flow and suppresses potential recombination channels, enabling near-unity charge utilization.