Piezocatalysis, a newly emerging catalysis technology that relies on the piezopotential and piezoelectric properties of the catalysts, is attracting unprecedented research enthusiasm for applications in energy conversion, organic synthesis, and environmental remediation. Despite the rapid development in the past three years, the mechanism of piezocatalysis is still under debate. A fundamental understanding of the working principles of this technology should enable the future design and optimization of piezocatalysts. Herein, we provide an overview of the two popular theories used to explain the observed piezocatalysis: energy band theory and screening charge effect. A comprehensive discussion and clarification of the differences, relevance, evidence, and contradiction of the two mechanisms are provided. Finally, challenges and perspectives for future mechanistic studies are highlighted. Hopefully, this Review can help readers gain a better understanding of piezocatalysis and enable its application in their own research.

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Piezocatalysis, a newly emerging catalysis technology that relies on the piezopotential and piezoelectric properties of the catalysts, is attracting unprecedented research enthusiasm for applications in energy conversion, organic synthesis, and environmental remediation. Despite the rapid development in the past three years, the mechanism of piezocatalysis is still under debate. A fundamental understanding of the working principles of this technology should enable the future design and optimization of piezocatalysts. Herein, we provide an overview of the two popular theories used to explain the observed piezocatalysis: energy band theory and screening charge effect. A comprehensive discussion and clarification of the differences, relevance, evidence, and contradiction of the two mechanisms are provided. Finally, challenges and perspectives for future mechanistic studies are highlighted. Hopefully, this Review can help readers gain a better understanding of piezocatalysis and enable its application in their own research.

Piezoelectric polarization portrays a promising technology to regulate the photogenerated charge carrier separation and transfer behaviors, and the design of multifunctional catalysts with piezo-phototronic effect is a key step. One strategy is to prepare a composite catalyst combining the ideal properties from each individual component. Herein, a facial dopantinduced self-assembling strategy is reported to fabricate an ultracompact nanocomposite (LaFeO 3 /ZnFe 2 O 4 /La 2 O 3 ) with enhanced efficiency for piezo-photocatalysis. The composite is synthesized at 800 °C from the one-pot method, thus the self-constructed interface is created during multi-phase formation, providing the intimate grain-to-grain contact between the semiconductive LaFeO 3 and piezoelectric ZnFe 2 O 4 /La 2 O 3 phases. In such a composite, a synergistic effect for oxygen activation is realized via the effective manipulation of the photogenerated charge carrier separation and spatial transportation through the vibration-created piezopotential. A high piezoelectric coefficient (d 33 ) up to 826 pm V −1 and a superior H 2 O 2 yield of 403 µmol g −1 h −1 (in open air and pure water) are achieved on the optimized composite, outperforming most of the reported lead-free piezo-photocatalyst. The ultracompact composite is very robust without any decay in H 2 O 2 -delivering capability after many cyclic tests.This study provides a universal strategy for the rational design of highperformance piezo-photocatalysts.

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