Photocatalytic properties of TiO2: Effect of niobium and oxygen activity on partial water oxidation

• Photocatalytic properties are determined by structural defects.
• Photoreactivity of water with TiO2 is determined by the concentration of titanium vacancies.
• Titanium vacancies are the surface active sites responsible for water oxidation.

This work reports the effect of niobium (0–1 at%) on photocatalytic activity and the band gap of TiO2 with controlled oxygen activity in the range 10−12 Pa < p(O2) < 105 Pa. It is shown that maximum of photocatalytic performance in partial water oxidation is observed for Nb-doped TiO2 containing 1 at% Nb that is processed at 1273 K in pure oxygen, p(O2) = 105 Pa. The mechanism of photocatalytic water oxidation is considered in terms of a predominant effect of photocatalytically active surface sites corresponding to titanium vacancies. It is shown that the niobium-induced increase of the band gap, surface potential and charge transport have a minor influence on photoreactivity of Nb-doped TiO2 with water.

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