121Sb Mössbauer spectroscopic insight into the puzzling persistence of photocatalytic activity exhibited by Sb-doped anatase TiO2

The unexpected behavior of Sb-doped anatase TiO₂ photocatalysts can be accounted for by their synthesis procedure involving thermal decomposition of a coprecipitated hydroxide precursor. This treatment results in the formation of titanium vacancies V_Ti which balance the excessive positive charge of Sb^V atoms in a way not affecting the wide-gap nature of anatase TiO₂ semiconductor. Nevertheless, V_Ti vacancies can also reduce its photocatalytic efficiency acting along with the oxygen ones V_O as supplementary recombination centers of photogenerated electrons and holes.