Manipulating the charge separation via piezoelectric field and heterojunction to enhance the photoelectrochemical water splitting ability of Bi2WO6/BiOBr photoanode

The unsatisfactory separation efficiency of photogenerated charge is one of the significant problems restricting the application of photoelectrochemical water splitting. Herein, we successfully prepared a Bi2WO6/BiOBr nanoplate arrays structure with the heterostructure for efficient piezoelectric photoelectric water splitting. A charge transfer path is formed by constructing a heterojunction to accelerate the spatial separation of photogenerated charges. The Bi2WO6/BiOBr shows the better photoelectrochemical performance with high photocurrent density of 0.068 mA/cm2 at 1.23 V vs. RHE which is 1.8 times higher than simple Bi2WO6. In addition, after the introduction of piezoelectric polarization, the carrier separation efficiency is further enhanced under the synergistic action of the piezoelectric polarization and the heterojunction, and the photocurrent of Bi2WO6/BiOBr photoanode is increased to 0.088 mA/cm2 at 1.23 V vs. RHE. By comparing the photoelectrocatalytic performance of the samples before and after the introduction of piezoelectric field, it further explains the role of piezoelectric built-in electric field in promoting carrier separation. This work provides a new method to improve the carrier separation efficiency by combining heterojunction and piezoelectric polarization.