Role of Cu in the Cu-TiO2 photocatalytic degradation of dihydroxybenzenes

The photocatalytic degradation of three dihydroxybenzenes (hydroquinone, catechol and resorcinol) by TiO 2 and Cu-TiO 2 has been studied. Degradation rates depend on the molecule catalyst surface interaction type. FTIR studies have shown that Cu presence modifies the organics interactions with the catalysts surface. Therefore, catalysts have shown different types of behaviour with each compound. Resorcinol interaction with Cu-TiO 2 may produce a hydroxyphenolate thus reducing the number of activating centres in the aromatic ring. However, catechol interaction provides a catecholate bidentate which virtually deactivates the aromatic ring, hence reducing its degradation by OH radicals attacks. Hydroquinone interaction with Cu-TiO 2 occurs by means of a hydrogen bond, while with TiO 2 this interaction is established through the formation of a hydroxyphenolate monodentate. This justifies the improved catalytic behaviour of Cu-TiO 2 . Studies in presence of H 2 O 2 have shown the existence of similar degradation mechanisms, but degradation rates have been notably higher.