Coupling defect-inherent built-in electric fields to promote directional charge migration for rapid photocatalytic degradation of levofloxacin

By enhancing the intrinsic built-in electric field (IEF) of the catalyst through defect engineering, and coupling the IEF of the catalyst via an S-type heterojunction structure, a 3-in-1 IEF is formed, which drives the directional migration of electrons and holes, and can effectively improve photocatalytic performance. In this paper, an oxygen vacancy-type Bi₂WO₆ (Ov-BWO) composite with twin-type Zn_0.5Cd_0.5S (ZCS) was synthesized to construct an S-scheme heterojunction. The twin structure results in an IEF in ZCS that points from the twin plane Zn to the twin boundary S. The oxygen vacancies, on the other hand, create an internal electric field from Bi and W to O by altering the local charge density. By coupling the IEF of the catalyst through the S-type heterojunction, an enhanced IEF is formed, pointing from the twin plane Zn to the O in Ov-BWO, enabling rapid directional migration of photogenerated charge carriers. Furthermore, potential Levofloxacin (LVFX) intermediates and degradation pathways were found by combining Liquid chromatography-mass spectrometry (LC-MS) data with Density Functional Theory (DFT) simulations. This study systematically elucidates the photocatalytic degradation system, from catalyst design to the degradation process of pollutants, through the analysis of theoretical calculations and experimental results.