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The secondary recombination of photogenic charge carriers caused by structural defects at the interface of BaTiO 3 /KNbO 3 heterojunction is successfully suppressed by the built-in electric field generated by the piezoelectric effect in BaTiO 3 and KNbO 3. BaTiO 3 /KNbO 3 composite photocatalyst exhibits excellent degradation performance for direct lake blue 5B dye (DLB 5B) under the synergistic effect of piezocatalysis and photocatalysis. [Display omitted] • BaTiO 3 /KNbO 3 heterostructure photocatalysts were successfully prepared for the first time. • BaTiO 3 /KNbO 3 presented good piezo-photocatalytic activity in degrading direct lake blue 5B dye under light irradiation and ultrasonic vibration. • The synergistic effect of piezocatalysis and photocatalysis on the separation and transfer of charge carriers was proposed. In order to reduce the secondary recombination of photogenic charge carriers caused by the structural defects at the interface of traditional heterostructure photocatlysts, and the charge shielding effect of static condition on the built-in electric field in ferroelectric/piezoelectric photocatalyst, two typical piezoelectric photocatalysts, BaTiO 3 and KNbO 3 , were successfully compounded into a series of BaTiO 3 /KNbO 3 heterostructure photocatalysts for the first time. BaTiO 3 nanoparticles with good crystallinity are uniformly distributed on the surface of KNbO 3 prism to form the BaTiO 3 /KNbO 3 heterostructure. The piezo-response force microscopy (PFM) results and piezo-photocatalytic degradation experiments stimulated by ultrasonic vibration and light irradiation show that the separation efficiency of photogenic charge carriers and degradation performance are enhanced by the synergistic effect of piezocatalysis and photocatalysis. The piezo-photocatalytic degradation efficiency of BaTiO 3 /KNbO 3 over direct lake blue 5B dye can reach up to 93.3%. The reaction rate constant of 0.3BaTiO 3 /0.7KNbO 3 over the target dye is 4.44 and 8.57 times higher than that of BaTiO 3 and KNbO 3. This work will provide a promising paradigm to degrade organic pollutants by using synergetic effect of piezocatalysis and photocatalysis, which perhaps facilitates the practical applications of piezo-photocatalytic technology in the environmental field. [ABSTRACT FROM AUTHOR]