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Domain observation in the visible-light photocatalyst Bi4NbO8Br with the layered perovskite structure

Layered perovskite oxyhalides Bi4MO8X (M = Nb, Ta; X = Cl, Br) are promising visible-light photocatalysts for water splitting, where the polar structure may enhance the conductivity of photocarriers. In this study, the domain structure of Bi4NbO8Br single crystal was investigated using piezoresponse force microscopy and transmission electron microscope. We observed a rare domain structure with a ferroelectric 180° domain in the nanoscale ferroelastic 90° domains developed in the ab plane. We also discuss the effect of these domain structures on the dynamics of photocarriers, which may provide new ideas for the design of highly active photocatalyst.