Piezoelectric Polarization Assisted Surface Defect Engineering to Improve BiVO₄ Photoelectrochemical Water Splitting

Manipulating the catalyst body and surface photogenerated charge separation is significant in expanding research in the field of photoelectrochemical water splitting. This paper introduces a certain amount of Bi-vacancies at the BiVO₄ photoanode by in-situ photoreduction and makes rational use of polarization field engineering to promote the separation of surface photogenerated carriers. Focusing on comparing the photoelectrochemistry (PEC) performance of BiVO₄ with different concentrations of Bi-vacancies under piezoelectric polarization field. At 1.23 V vs. RHE, the photocurrent density of the best sample is 0.147 mA/cm², which is 1.8 times higher than that of BiVO₄. In addition, the photocurrent density reached 0.162 mA/cm² under ultrasonic conditions. The presence of a moderate amount of Bi-vacancies provides a large number of active sites, which lowers the potential barrier for redox reactions thereby reducing the resistance to electron leaps, decreasing the forbidden bandwidth and increasing the light absorption range. The piezoelectric polarization field is triggered by ultrasonic conditions, and the cavitation bubbles are ruptured by ultrasonic vibrations, generating a large amount of charge involved in the water splitting reaction. The presence of surface vacancies makes the piezoelectric polarization easier to be triggered, and the enhanced built-in piezoelectric field acts as a driving force to improve the interfacial separation and transport efficiency of photogenerated carriers, which effectively improves the PEC performance. This work provides a new and scientifically sound idea for the combined use of vacancy defect engineering and piezoelectric effect in the field of PEC splitting water.