Impact of ferroelectricity on the photodegradation of charged dye species: significance of polarity match

Ferroelectric materials as photocatalysts are attracting growing attention, as their spontaneous polarization is likely to have positive impacts on photocatalysis due to the improved charge-separation which was evidenced by studies on the influence of polarization on the degradation of Rhodamine B (Rh B). In this work, we investigated the effect of polarization on the photocatalytic activity of BaTiO3 for the decolorization of methyl orange whose chromophoric species carry charges with opposite polarity to that of Rh B in aqueous solution, and found that the ferroelectricity had a negative effect. A mechanism taking into account not only the charge separation but also the preferential adsorption of charged dye species in the aqueous solution on the polar surfaces of ferroelectric particles has been proposed to explain the observed phenomenon. The results unravel the importance of polarity match between the chromophoric species of the dye in the aqueous solution and the photo-induced charge carriers responsible for the photocatalysis.