Novel antimonate photocatalysts MSb₂O₆ (M = Ca, Sr and Ba): a correlation between packing factor and photocatalytic activity

Well-crystallized MSb₂O₆ (M = Ca, Sr and Ba) powders synthesized by solid state reactions exhibit an interesting photocatalytic activity order of Ba > Sr > Ca for organic pollutant (methylene blue and phenol) degradation and hydrogen production from water under UV light irradiation. A simple model, crystal packing factor (PF), was introduced to account for the activity difference. Nine series of photocatalysts involving 26 compounds were experimentally investigated to further substantiate the model, a lower PF being correlated to a higher photocatalytic activity. This correlation between packing factor and photocatalytic activity also holds for some 40 literature examples of 83 compounds of d⁰ cations and d¹⁰ cations. This applicable criterion for ranking photocatalytic materials of similar chemistry or structure can be rationalized through the influence of structural packing on carrier lifetimes and mobilities.