Effect of Sb⁵⁺ codopant ions on the ultraviolet photocatalytic activity of Fe³⁺-modified anatase

The presence of antimony in (x at% Fe³⁺ + x at% Sb⁵⁺):TiO₂ powder samples containing equimolar amounts (0.15 ≤ x ≤ 1) of the dopant cations was accompanied by an increase in the reaction rate constant k of the decolorization of methyl orange. Nevertheless, the increase in the rate of this test reaction, consistent with a decrease in the number of charge balance oxygen vacancies VO imputable to the codoping with Sb⁵⁺, rapidly weakened with increasing x. This effect is accounted for by the increased number of Fe³⁺–VO associates slowing down the outward diffusion of VO vacancies and, consequently, their rate of annealing in the studied catalyst.