Ferroelectric Polarization‐Induced Performance Enhancements in BiFeO3/BiVO4 Photoanodes for Photoelectrochemical Water Splitting

Abstract Photoelectrochemical (PEC) processes will play a crucial role in future clean energy systems, however severe charge recombination and sluggish charge transfer kinetics have hindered their practical adoption. Exploiting ferroelectric polarization‐controlled charge dynamics promises an additional lever that can potentially enable the performance limits of traditional static photoelectrodes to be surpassed. Here one of the most notable ferroelectric polarization‐induced photocurrent enhancements is reported, using a heterostructure of the multiferroic bismuth ferrite (BFO) and the photoactive bismuth vanadate (BVO) in a neutral pH electrolyte. In contrast to previous works, enhancements for both poling directions are reported, of 136% for down‐poled BFO/BVO and 70% for up‐poled BFO/BVO at 1.23 V RHE in comparison to the unpoled sample, delivering a Faradaic efficiency of >95% for prolonged oxygen evolution reaction. Extensive PEC and surface analyses complemented by density functional theory (DFT) calculations reveal the improvements are attributed to the modulation of gradients in the BFO band energies, as well as changes in band‐bending and offsets at the interfaces. Given the scalability of the employed sol–gel synthesis method and the use of environmentally benign materials and PEC conditions, these findings pave the way for multifunctional materials as new‐generation agile and dynamic catalysts and photoelectrode systems.