Piezotronic effect boosted photocatalytic performance of NiO@PbTiO3 p-n heterojunction

The built-in electric field existing in heterojunction of hybrid photocatalyst is favorable to separate the photogenerated carriers in photocatalytic reaction. Besides, the electric field existing in the whole ferroelectric bulk can also effectively separate the photogenerated carriers. Here the catalytic reaction is enhanced through the enlarged electric field contributed by both p-n junction and the ferroelectric polarization. A new composite is prepared with the n-type single-crystal PbTiO 3 nanoplate coated with the p-type NiO particles, and its photocatalytic degradation rate of RhB (0.253 min −1 ) is 4.71 times of pure PbTiO 3 (0.0537 min −1 ) due to the contribution of p-n junction. In addition, the piezo-phototronic effect is applied to further enhance the photocatalytic performance. Under light and ultrasonic excitation, the screening effect of ferroelectric polarization can be broken by the alternating piezoelectric potential due to the periodic mechanical stress, and thus the reaction rate of piezo-photocatalytic degradation of RhB (0.461 min −1 ) is 1.82 times of photocatalytic reaction rate (0.253 min −1 ) for NiO@PbTiO 3 composite and 3.34 times of the piezo-photocatalytic reaction rate for pure PbTiO 3 (0.138 min −1 ). This work is helpful to clarify the piezo-photocatalytic mechanism and develop efficient photocatalysts.