Phosphate ions improve the performance of BiFeO3 piezoelectric photoelectrochemical water splitting

Abstract

Enhancing the piezoelectric polarization strength of materials to promote the photogenerated carrier separation is of great significance for piezoelectric polarization-assisted photoelectrochemical (PEC) water splitting. In this paper, P-BiFeO₃ composite photoelectrodes were synthesized by modifying BiFeO₃ photoelectrodes with phosphate ions. The maximum photocurrent density of the P-BiFeO₃ composite photoelectrodes could reach 0.87 mA cm⁻² at 1.23 V vs RHE, which is significantly enhanced compared to the BiFeO₃ photocurrent. The enhanced photoelectrochemical activity of the phosphate ion-modified BiFeO₃ photoelectrodes may be attributed to the increased visible light absorption and larger active area due to the presence of phosphate groups. Furthermore, the photocurrent density of the P-BiFeO₃ composite photoelectrodes after the introduction of the piezoelectric polarisation field reached 2.58 mA cm⁻² at 1.23 V vs RHE, which was 2.2 times higher than that of BiFeO₃ (1.17 mA cm⁻²). The presence of phosphate groups on the surface of BiFeO₃ photoelectrodes can improve their asymmetry and increase their piezoelectric polarisation intensity, further enhancing the PEC water splitting performance of the material. This study provides a strategy for the design of highly active photoanodes with ionic modification to enhance the piezoelectric polarisation of the material to improve PEC water splitting.