Ferroelectric Polarization-Induced Performance Enhancements in BiFeO3-Based Photoanodes for Photoelectrochemical Water Splitting

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 we report one of the most notable ferroelectric polarization-induced photocurrent enhancements, 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, we report enhancements for both poling directions, of 136% for down-poled BFO/BVO and of 70% for the up-poled BFO/BVO, at 1.23 VRHE in comparison to the unpoled, delivering a Faradaic efficiency of more than 95% for prolonged oxygen evolution reaction. Extensive PEC and surface analyses complemented by DFT calculations reveal the improvements are attributed to the modulation of gradients in BFO band energies, 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, our findings pave the way for multifunctional materials as new-generation agile and dynamic catalyst and photoelectrode systems.