Multidomain simulations of coated ferroelectrics exhibiting spatially selective photocatalytic activity with high internal quantum efficiencies
The internal quantum efficiency (IQE) of multidomain ferroelectric BaTiO3 coated with thin (10 nm) anatase TiO2 films has been modeled in two dimensions, using physically reasonable property values of each material. The minority carrier current density averaged across the entire surface, composed of equal portions of positively and negatively polarized domains separated by 180° boundaries, is similar to that reported previously for a single negatively polarized domain (modeled in one dimension). This indicates that photogenerated carriers driven away from the surface in one domain can be collected at the surface of the neighboring domain and participate in surface reactivity. For a wide range of physically reasonable domain widths, from approximately 100 to 400 nm, the limiting IQE is more than 90% of the maximum value, and far exceeds that for Z-scheme domain reactivity, where the carriers driven away from the surface would recombine in the bulk. When the potential and the domain width of alternating positively and negatively polarized domains are optimized, the balancing reduction and oxidation currents occur on the surface with a total limiting IQE as high as 90%, implying there exists significant room for improvement of photocatalysts using spatially varying internal fields at or near the reactive surface.