J. Photochem. Photobiol. A, Chem. 110(3) [299-307](1997)

ESR Investigation into the Effects of Heat Treatment and Crystal Structure on Radicals Produced over Irradiated TiO₂ Powder.

Yasuhiro Nakaoka and Yoshio Nosaka

(Abstract)

ESR measurements were carried out at 77 K under irradiation for anatase TiO₂ powders treated by heating at various temperatures in the air. For the untreated powder photoproduced holes were trapped at the surface forming Ti⁴⁺O^-.Ti₄⁺OH^- radicals, while, for the heated powder, they were trapped as Ti⁴⁺O^2-Ti⁴⁺O^-. radicals at the surface. Photoproduced electrons were trapped as Ti³⁺ at the surface of the unheated powder, while they trapped at the inner part of the heat-treated powder. These differences could be explained by the desorption of surface hydroxyl groups and the change in the surface structure accompanied by the crystalline growth. No photoproduced radicals were detected for rutile TiO₂ powder, which may explain the low photocatalytic activity of this crystalline structure.

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