Semiconducting piezoelectric heterostructures for piezo- and piezophotocatalysis

Piezoelectric semiconductors can be polarized and used in mechanoredox systems and photoredox catalysis. Conventional non-piezoelectric semiconductors have limitations when it comes to charge carrier recombination and slow transport rates in catalytic reactions, which can be overcome by piezoelectric polarization processes in piezoelectric semiconductors. Heterostructures based on semiconducting piezoelectrics often offer enhanced catalytic reactivities that are related to their mechanical, piezoelectric, optical, and electronic characteristics. We review how to use such heterostructures to convert mechanical energy into chemical energy, and how the related piezoelectric polarization tunes the band structures and provides advantages in piezophotocatalysis over regular photocatalysis. We discuss fundamental concepts of piezoelectricity, piezoelectric potential, and examine different piezoelectric heterostructures for piezoand piezophotocatalysis. A review of dynamic investigations of piezoand piezophotocatalytic processes is presented. The complementary developments in the understanding of the piezotronic and piezophototronic effects are described, which include the induced charge-transfer mechanisms for piezoand piezophotocatalytic reactions that can occur with piezoelectric heterostructures. Finally, we derive design principles and suggest future research directions in the emerging field of piezoand piezophotocatalysis employing semiconductive heterostructures.