TiO2 photocatalysts activated by acid or base treatments for aromatic alcohols oxidation

Anatase TiO2 samples (Merck and BDH) were treated in acid or basic solutions at different temperatures and tested for the photocatalytic partial oxidation of 3-pyridinemethanol, 4-methoxybenzyl alcohol and 5-(hydroxymethyl)-2-furaldehyde in environment friendly conditions. Catalysts characterization has been carried out by XRD, TGA, BET, TEM, Photoluminescence, FT-IR, Raman, DRS and Photocurrent analyses. The acid and basic treated samples showed higher photocatalytic activity than the untreated ones; the products yields greatly increased even though the treatments did not improve the selectivity towards the partial oxidation products. Efficient photocatalytic degradation of 4-nitrophenol was also performed to show that these catalysts could be used for degradation of harmfull substrates. In order to further improve the acid or alkaline traated samples activity, Pt was used to decorate both untreated and treated TiO2; Pt acts as electron scavenger leading to the electrons transfer from TiO2 conduction band to Pt clusters, thereby boosting the number of photogenerated pairs available for the reaction process. Pt loading determined an improvement of samples reactivity as much as the acid and basic treatment did. Treated catalysts significantly maintained their reactivity performances even after a thermal treatment at 700 °C. The catalysts structural characterization showed that the disordered layer present on anatase crystals surface increased by acid and basic treatment. Photoluminescence and photocurrent analyses show that the recombination rates of e-/h+ on the catalysts surface were not changed by acid or alkaline effect, while photoactive sites on the photocatalyst surface were increased significantly.