Synergistic effect of built-in and polarized electric fields in BiFeO3/BiOI heterojunctions for efficient photocatalysis†

Abstract

The built-in electric field (IEF) between two components of a heterojunction has been proven to be capable of efficiently separating photogenerated carriers in photocatalysis. However, the rapid charge accumulation near the interface of the heterojunction tends to neutralize this electric field, resulting in the deterioration of the heterojunction performance. Herein, ferroelectric-based BiFeO₃/BiOI-n heterojunctions (BFO/BiOI-n) were prepared utilizing epitaxial growth. BFO not only endows the heterojunctions with stronger ferroelectric polarization, which was confirmed by the hysteresis loop, but also induces a significant redistribution of carriers, which maintains a stronger IEF in BFO/BiOI-n. Furthermore, the ferroelectric polarization of BFO was further regulated via corona poling and the enlarged ferroelectric polarization was also favorable to improve the photocatalytic performance. The optimal PBFO/BiOI-4 sample delivers complete degradation of RhB within 30 minutes and a hydrogen evolution rate of 150 μmol g⁻¹ h⁻¹. The significantly improved photocatalytic performance is attributed to the efficient photogenerated carrier separation synergistically promoted by the IEF in the heterojunction and the polarized electric field (PEF) in BFO. This work provides a feasible scheme for designing ferroelectric-based heterojunction photocatalysts.