Surface reactivity of reduced titanium dioxide

A moderate surface reduction of TiO2(anatase or rutile) at 573–773 K under vacuum, or in the presence of carbon monoxide or hydrogen, or finally at room temperature under ultra-violet irradiation in vacuum or in the presence of hydrocarbons, creates two types of paramagnetic centres, which are identified by e.s.r. spectra as Ti3+ ions.Adsorption of oxygen (between 77 and 373 K) on TiO2 samples reduced in the ways described above leads to the formation of ionic species of the type O–2. The same species are also formed at room temperature on unreduced TiO2 samples submitted to an UV irradiation in the range of 2000–6000 A.These results are paralleled with the occurrence of photocatalytic (in u.-v.) partial oxidation of isobutane on TiO2 at room temperature.