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The strategy of modulating polarization rotation of potassium sodium-niobate ((K 0.5 Na 0.5)NbO 3 , KNN) lead-free piezoelectric materials was reported to boost piezoelectric properties and resultant piezocatalytic activities. The effectiveness of modulating polarization rotation was proved by degrading Rhodamine B (RhB) using three KNN-based samples with different phase structures (i.e., orthorhombic (O) phase, orthorhombic-tetragonal (O-T) coexistence phase, and rhombohedral-orthorhombic-tetragonal (R-O-T) coexistence phase). Poled samples with the R-O-T coexistence phase show a reaction rate constant of 0.091 min−1 owing to the easiest polarization rotation, 2.12 times more than that of poled O-phase featured samples with the most difficult polarization rotation. Enhanced piezocatalytic activities primarily originate from the easier polarization rotation and improved carrier concentration, accompanied by the trace of the mechano-charge generation. Therefore, modulating polarization rotation effectively boosts piezocatalysis of KNN-based materials, promising for harnessing natural energy and disease treatment. [Display omitted] • lead-free (K, Na)NbO 3 materials are eco-friendly piezocatalyst. • Proposing a new strategy to enhance there piezocatalysis. • Obtaining a high k value of 0.091 min−1, much superior to those of other materials. • Unveiling the physical mechanisms of the superior piezocatalytic activities. [ABSTRACT FROM AUTHOR]