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Profiting from the piezoelectric effect, the CuInS2-BiFeO3 S-scheme heterojunction with eliminated interface shielding effect facilitates carrier separation and exhibits an excellent piezo-photocatalytic H2 evolution performance driven by the synergy of piezoelectric field and S-scheme built-in electric field. [Display omitted] • CuInS 2 -BiFeO 3 is constructed via a hydrothermal method with electrostatic self-assembly strategy. • Piezoelectric field eliminates the interface shielding effect within S-scheme heterojunction. • Synergistic utilization of built-in field and piezo-polarization field exhibits superior photocatalytic performance. 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 CuInS 2 -BiFeO 3 S-scheme heterojunction which with powerful piezoelectric field endowed by the piezoelectric BiFeO 3 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 CuInS 2 to BiFeO 3 has been confirmed by in-situ X-ray photoelectron spectroscopy and electron paramagnetic resonance. Furthermore, the obviously piezo-field at the interface of CuInS 2 -BiFeO 3 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 H 2 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. [ABSTRACT FROM AUTHOR]

Piezoelectric polarization can provide a strong driving force to accelerate the separation and migration of photo-generated carriers, enabling more electrons and holes to migrate to the surface of the Bi 3 TiNbO 9 nanosheets. Meanwhile, the piezo-potential will induce the band bending, which can adjust the band structure to enhance the redox abilities of catalyst. [Display omitted] • Bi 3 TiNbO 9 nanosheets were synthesized by an one-step hydrothermal method. • Piezocatalytic and piezo-photocatalytic performance of Bi 3 TiNbO 9 were explored. • Piezoelectric polarization accelerates the separation and migration of photocharges. • Bi 3 TiNbO 9 shows universal piezo-photocatalytic degradation performance and excellent durability. Photocatalysis is considered as a green and efficient technology for dealing with water pollution problems, but there exists serious carrier recombination in photocatalysis. Introducing a piezoelectric field to reduce carrier recombination and accelerate carrier separation and migration is a recognized as an effective approach, while it remains testing for exploitation for high-performance catalysts with light and stress dual response as well as the coupling catalytic mechanism. In this work, we report a novel layered perovskite structure piezo-photocatalyst Bi 3 TiNbO 9 and conducted an analysis of potential piezo-photocatalytic mechanisms. The piezoelectric force microscopy (PFM) and COMSOL finite element analysis prove that the Bi 3 TiNbO 9 is a piezoelectric with strong piezoelectricity. In the degradation of tetracycline hydrochloride, Bi 3 TiNbO 9 exhibits significantly better piezo-photocatalysis performance compared to piezocatalysis and photocatalysis. It is owing to that the ultrasound results in piezoelectric polarization accompanied by the generation of piezo-potential, which can induce piezocatalysis and facilitate the separation and transfer of photo-generated carriers. Electron paramagnetic resonance (EPR) technique and electrochemical tests are carried out under different excitation sources to identify the dominant active species involved in the reaction and to disclose the origin for the high performance of piezo-photocatalysis from the perspective of carriers. This study adds a new member to the family of piezo-photocatalytic material system, and provides further understanding on the synergistic piezo-photocatalysis mechanism. [ABSTRACT FROM AUTHOR]

Piezoelectric polarization and interfacial electric field are integrated in Bi 2 O 2 (OH)NO 3 -Bi 2 MoO 6 heterojunction photocatalysts synthesized via in situ transformation method, which synergistically promotes the piezo-photocatalytic activity. [Display omitted] • Bi 2 O 2 (OH)NO 3 -Bi 2 MoO 6 heterojunction with strong interfacial electric field is synthesized. • Introduction of ultrasound vibration provides piezoelectric polarization and effective piezocatalysis. • Interfacial electric field and piezoelectric polarization cooperatively promote the separation and transfer of photogenerated charges. • Bi 2 O 2 (OH)NO 3 -Bi 2 MoO 6 displayed efficient piezo-photocatalytic degradation of TC. Photocatalysis is a promising approach for purifying water pollutants resources, but is greatly restricted by rapid photogenerated charges recombination. Herein, Bi 2 O 2 (OH)NO 3 -Bi 2 MoO 6 heterojunction photocatalysts with strong interfacial electric field are synthesized via in situ transformation method with using Bi 2 O 2 (OH)NO 3 as a self-sacrificial template. The intimate interface interaction renders a large interfacial potential, which allows efficient charge separation within the heterojunction. Thus, the photocatalytic activity was well optimized compared with the pristine catalyst and composite counterpart prepared by in situ growth route. Then, the piezoelectric polarization induced by ultrasonic vibration is introduced in the photocatalytic system, which yields a piezocatalytic activity and enhancement on the separation and transfer of photogenerated charge carriers. Benefiting from the piezoelectric polarization and interfacial electric field, the in situ transformed Bi 2 O 2 (OH)NO 3 -Bi 2 MoO 6 heterojunction exhibits a prominent piezo-photocatalytic performance for degradation of tetracycline, much higher than that under sole light or ultrasound irradiation source as well as the individual catalyst. This work reveals the potential of the collaboration of piezoelectric polarization and interfacial electric field in photocatalysis. [ABSTRACT FROM AUTHOR]