Bi2WO6/spontaneously polarized ceramic‒g-C3N4 heterojunction with dynamic cascade electric fields to deplete unilaterally accumulated charges and break carrier shielding effect for boosting piezo-photocatalysis

Abstract

In photocatalysis field, S-scheme heterojunctions show unique advantages and prospects. However, the carrier shielding effect of heterojunctions limits the separation and migration of interfacial charges. In this study, a strategy of “dynamic cascade electric fields to deplete unilaterally accumulated charges” was innovatively proposed to overcome this drawback. By modulating g-C₃N₄ (CN) and Bi₂WO₆ (BWO) using the polarized electric field (PEF) of spontaneously polarized ceramic (SPC), a BWO/SPC-CN composite with cascade internal electric field (IEF) and PEF was successfully constructed for efficient piezo-photocatalytic degradation of recalcitrant pollutants. BWO/SPC-CN contributed to 96.8% degradation of carbamazepine, significantly surpassing BWO/CN (70.5%). BWO/SPC-CN performed excellent capacity of harvesting piezoelectric energy due to its unique three-dimensional porous nano-network structure. The PEF of SPC modulated the electronic band structure and thus strengthened the IEF of BWO/SPC-CN, providing a persistent driving force for interfacial charge migration. Moreover, SPC with a strong PEF unilaterally consumed the charges accumulated on CN under periodic piezoelectricity, weakening the shielding electric field to inhibit the recombination of electron‒hole pairs. As a consequence, the dynamic cascade PEF–IEF ultimately broke the carrier shielding effect in heterojunction photocatalysis and enhanced interfacial electron transfer. This work provides reliable methods to enhance the interfacial charge transfer in heterojunction and new insights into piezo-photocatalytic mechanism.