Piezoelectric field and defect engineering synergistically improved photocatalytic performance of K0.5Na0.5BixNb1-xO3 for degradation of organic pollutants

Semiconductor photocatalysts have been widely researched in wastewater treatment and photocatalysis predominantly depends on the redox reaction of photoinduced charge carriers on semiconductor surface. Afterwards, photoinduced carrier concentration and the effective separation of electrons and holes have been proved to be pivotal in promoting photocatalytic efficiency. Further, the internal electric field established by polarization of piezoelectric materials is considered an efficient means of separating electrons and holes. Hence, as a typical representative of piezoelectric materials, (K0.5Na0.5)Nb1-xBixO3 was designed and prepared by introducing Bi2O3 in (K0.5Na0.5)NbO3 to construct defects intentionally, and thus reduce the band gap and increase carrier concentration by the hybrid energy levels, for another promote efficient separation of electrons and holes by virtue of the built-in field created by piezoelectric polarization and pinning holes by defects. Thereinto, the K of Rh B degradation by (K0.5Na0.5)Bi0.02Nb0.98O3 reached 0.07846 min−1 under the combined light irradiation and ultrasonic, meanwhile 95 % Rh B can be degraded within 20 min and nearly 100 % in 60 min with eminent cycling stability, which is brilliant than previous reports on KNN-based catalyst. This work provides not only a novel piezo-photocatalytic degradation material but also a built-in electric field and defect synergy strategy for boosting carrier separation.