Effect of Lewis acid centres and H2O2-complexes on the photocatalytic degradation of phenol

A Ti–H2O2–phenol complex, not described until now, has been identified on the surface of Degussa P-25 and the new catalyst ECT-1023. This complex is considered to be responsible for the higher hydroquinone to catechol concentration ratio. It has been also shown that phenolates identified on the surface modify electrodonation that controls the generation of activating positions of the aromatic ring. The different strengths of the Lewis acid centres identified provide phenolates with different electrodonation ability. It has been observed that P-25 has Lewis acid centres with stronger acid character than those of ECT-1023. Thus, the mechanism of phenol degradation is affected by the formation of complexes with H2O2 and the distribution and strength of Lewis acid centres of the studied catalyst.

► A new Ti–H2O2–phenol complex has been identified on the surface of TiO2.
► This complex alters the distribution of the hydroxylated phenolic intermediates.
► A new mechanism for phenol photocatalytic degradation has been proposed.
► Lewis acid centres strength has been correlated with catalyst photoactivity.