Carrier spatial decoupling in ZnIn2S4/Bi5O7I heterojunction via interfacial chemical bonding mediated band edge reorganization for efficient Photocatalysis

Interfacial chemical bonding can induce band edge reorganization in heterojunctions, profoundly altering their photocatalytic mechanisms, but such mechanisms are rarely reported. In this study, an interfacial chemical bonding heterojunction ZnIn 2 S 4 /Bi 5 O 7 I (ZIS/BOI) was successfully synthesized. The degradation kinetic constant of ZIS/BOI for metronidazole was 2.38 times higher than that of pristine ZIS. Experimental characterizations and density functional theory calculations revealed that Bi S bonds were formed at the ZIS/BOI interface by p-p orbital overlap, which induced the reorganization of the band edges of ZIS and BOI. The valence band maximum was localized on BOI, while the conduction band minimum was distributed on ZIS, achieving spatial decoupling of charge carriers and resulting in superior carrier separation efficiency, thereby enhancing the photocatalytic reaction performance. Moreover, a correlation model between pollutant molecular structure and photocatalytic degradation performance was established, revealing that molecular dipole moment was the most important factor determining degradation efficiency. This study demonstrated that interfacial chemical bonding can modify the energy band structure of heterojunctions, where originally independent band edges from different semiconductors merge into a unified set of band edges, thereby yielding a novel photocatalytic mechanism. The findings offer a new theoretical basis for designing high-performance interfacial chemical bonding heterojunction photocatalysts.