Spin polarization and interface electric field synergistically promote charge separation and photocatalytic performance: Intermediate, toxicity and mechanism

The separation efficiency of photogenerated carriers at the interface electric field of Z-scheme heterojunctions remained unsatisfactory and could be improved by introducing spin polarization. Herein, 0D Mn0.6Zn0.4Fe2O4 (Mn0.6ZFO) nanoparticles were selected to construct a Z-scheme heterojunction with 2D Bi12O17Cl2 (Bi12) that synergistically utilizes spin polarization to enhance charge separation and photocatalytic performance. The 0D/ 2D Mn0.6ZFO/Bi12 composites were exposed to tetracycline (TC) with and without an external magnetic field to test the photocatalytic degradation performance. Notably, under conditions without a magnetic field, the Mn0.6ZFO/Bi12 composite with a mass ratio of 1:2 (1 M:2B) exhibited the best performance, with a reaction rate constant k of 0.050 min(-1). Its catalytic efficiency was enhanced by approximately 2.85 times compared to Mn0.6ZFO (0.013 min(-1)) and by about 0.92 times compared to Bi12 (0.026 min(-1)), which is related to the charge separation effect in the Z-scheme heterojunction. The modulation of a magnetic field further improved the performance of the 1 M:2B composite by approximately 30 %, with the reaction rate constant k reaching 0.064 min(-1). This enhancement was attributable to the synergistic improvement of charge separation efficiency through electron spin polarization in conjunction with the Z-scheme heterojunction. Cycling experiments further demonstrated the stability and applicability of 1 M:2B. In addition, the possible TC degradation pathway and intermediate toxicity were investigated, and mung bean cultivation experiment indicated that the toxicity of TC solution was reduced. The photocurrent and electrochemical impedance spectroscopy (EIS) indicated that the composite exhibited a stronger charge separation ability. This study provided a novel approach for enhancing charge separation through the synergistic effect of Z-scheme heterojunctions and spin polarization.