Eliminating interface shielding effect endowed by piezoelectric polarization in S-scheme heterojunction for high-efficiency H2 evolution

Abstract

Eliminating the interface shielding effect within step-scheme (S-scheme) heterojunctions which can attenuate the separation driving force of built-in electric field plays a vital role in enhancing the photocatalytic performance. Herein, an extra driving force induced by piezoelectric field is introduced to mitigate such predicament in S-scheme, thereby facilitating the charge separation. Specifically, the piezoelectric CuInS2-BiFeO3 S-scheme heterojunction which with powerful piezoelectric field endowed by the piezoelectric BiFeO3 is constructed via a facile electrostatic self-assembly strategy and served as the touchstone to verify that hypothesis. The direction of built-in field between the heterojunction interface that is orienting from CuInS2 to BiFeO3 has been confirmed by in-situ X-ray photoelectron spectroscopy and electron paramagnetic resonance. Furthermore, the obviously piezo-field at the interface of CuInS2-BiFeO3 which can tilt energy band to enhance the built-in field under external force is also revealed by piezoresponse force microscopy. Consequently, benefiting from the highly-efficient charge separation offered by the synergy of piezoelectric field and S-scheme built-in electric field, a remarkably H2 production rate of 1465.1 µmol/g is achieved under simultaneous visible light and ultrasonic vibration irradiation. This work sheds light on the role of external field in enhancing the efficient separation of carriers in S-scheme heterojunctions.