Phosphate ions improve the performance of BiFeO3 piezoelectric photoelectrochemical water splitting

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.