Unlocking the “Piezocatalytic Sweet Spot”: A Synergistic Match of System‐Wide Energy Capture and Unit‐Level Piezoelectricity for Efficient H ₂ O ₂ Production

ABSTRACT Piezocatalysis provides a promising mechanically driven route for decentralized H 2 O 2 production, yet its efficiency is constrained by the inherent size trade‐off between system‐level mechanical energy harvesting and unit‐level piezoelectric output. In this study, the concept of a “piezocatalytic sweet spot” is identified and validated. A model system of ZnO NRs is constructed with strictly uniform crystallinity, defect density, and morphology and with a gradient in size, and the optimal size (ZnO NR 3 ) achieving maximum performance is obtained by balancing the above competing factors, yielding an H 2 O 2 production rate of 803 µmol g −1 h −1 . Multiscale investigation reveals that the “sweet spot” originates from the optimal synergy between system‐level mechanical energy capture and unit‐level piezoelectric output at a specific size, enabling efficient conversion of mechanical energy into localized piezopotential. Further investigation demonstrates that the piezopotential facilitates the spatial enrichment of charges onto highly active polar (001) facets. These facets, leveraging their superior oxygen adsorption capacity and stabilization of the •O 2 − intermediate, drive the two‐electron oxygen reduction pathway, ultimately achieving efficient directional conversion of mechanical energy into chemical energy. This work provides a universal optimization strategy for designing high‐performance piezocatalysts and facilitating mechanically driven chemical energy conversion through synergistic parameter design.