Doping of W Ions to Modulate the Polarization Intensity of Bi₂WO₆ for Efficient Piezoelectric–Photoelechochemical Water Splitting

The built-in electric field induced by piezoelectric polarization is an important method to effectively improve the inefficient charge transport of photoelectrochemical (PEC) water splitting. Here, we introduce a certain amount of W5+ into Bi2WO6 crystal to modulate its piezoelectric polarization performance, thus improving its piezoelectric internal electric field to drive the separation of carriers to improve the piezoelectric photoelectrochemical (piezo-PEC) water splitting. The doping of W5+ ion widens the visible light response of the sample on the one hand, and increases the free charge density in Bi2WO6 nanosheets on the other hand, thereby improving the charge transfer efficiency. The Bi2WO6-2 sample exhibits the best photochemical properties, and the photocurrent density was 0.126 mA/cm2 at 1.23 V vs RHE. In addition, under ultrasonic conditions, the current of the Bi2WO6-2 photoelectrode was enhanced to 0.181 mA/cm2 at 1.23 V vs RHE. The effect of ion doping on piezo-PEC performance was further explained by comparing the PEC performance of the samples before and after the introduction of the piezoelectric built-in electric field. This work suggests future uses for Bi2WO6 piezo-PEC water splitting.