BaTiO 3 is used as a target catalyst to probe the influence of ferroelectricity on the decolorization of a typical dye moleculeRhodamine Bunder simulated solar light. We show that there is a 3-fold increase in the decolorization rate using BaTiO 3 with a high tetragonal content compared to predominantly cubic material. This is ascribed to the ferroelectricity of the tetragonal phase. The influence of ferroelectricity ensures a tightly bound layer of dye molecule and also acts to separate the photoexcited carriers due to the internal space charge layer. Both of these features act to enhance the catalytic performance. When nanostructured Ag is photochemically deposited on the surface of the BaTiO 3 , we find a further increase in the reaction rate that gives complete decolorization of the dye in around 45 min.

We have used a ferroelectric BaTiO substrate with a hematite (α-FeO) nanostructured surface to form a heterogeneous BaTiO/α-FeO photocatalyst. In this study we show that varying the mass ratio of α-FeO on BaTiO has a significant influence on photoinduced decolorization of rhodamine B under simulated sunlight. The highest photocatalytic activity was obtained for BaTiO-FeO-0.001M, with the lowest mass ratio of α-FeO in our study. This catalyst exhibited a 2-fold increase in performance compared to pure BaTiO and a 5-fold increase when compared to the higher-surface-area pure α-FeO. 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 BaTiO 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.

Reaction mechanism for RhB degradation over a self-polarised semiconductor, BaTiO3.