121Sb Mossbauer 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 VTi which balance the excessive positive charge of SbV atoms in a way not affecting the wide-gap nature of anatase TiO2 semiconductor. Nevertheless, VTi vacancies can also reduce its photocatalytic efficiency acting along with the oxygen ones VO as supplementary recombination centers of photogenerated electrons and holes.