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

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 Sscheme, 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 highlyefficient charge separation offered by the synergy of piezoelectric field and S-scheme built-in electric field, a remarkably H2 production rate of 1465.1 mu mol/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.