Enhanced Photocatalytic Activity of Heterostructured Ferroelectric BaTiO₃/α-Fe₂O₃ and the Significance of Interface Morphology Control

We have used a ferroelectric BaTiO₃ substrate with a hematite (α-Fe₂O₃) nanostructured surface to form a heterogeneous BaTiO₃/α-Fe₂O₃ photocatalyst. In this study we show that varying the mass ratio of α-Fe₂O₃ on BaTiO₃ has a significant influence on photoinduced decolorization of rhodamine B under simulated sunlight. The highest photocatalytic activity was obtained for BaTiO₃-Fe₂O₃-0.001M, with the lowest mass ratio of α-Fe₂O₃ in our study. This catalyst exhibited a 2-fold increase in performance compared to pure BaTiO₃ and a 5-fold increase when compared to the higher-surface-area pure α-Fe₂O₃. The increases in performance become more marked upon scaling for the lower surface area of the heterostructured catalyst. Performance enhancement is associated with improved charge-carrier separation at the interface between the ferroelectric surface, which exhibits ferroelectric polarization, and the hematite. Increasing the mass ratio of hematite increases the thickness of this layer, lowers the number of triple-point locations, and results in reduced performance enhancement. We show that the reduced performance is due to a lack of light penetrating into BaTiO₃ and to relationships between the depolarization field from the ferroelectric and carriers in the hematite. Our findings demonstrate that it is possible to use the built-in electric field of a ferroelectric material to promote charge-carrier separation and boost photocatalytic efficiency.