Study of the synergic effect of sulphate pre-treatment and platinisation on the highly improved photocatalytic activity of TiO2

An important improvement of the photocatalytic activity of sol-gel prepared TiO2 has been achieved by sulphate pre-treatment, calcination at high temperature and further platinisation of the samples. The presence of sulphuric acid clearly stabilised TiO2 surface area against sintering, maintaining at the same time anatase phase until higher calcination temperatures than in non-sulphated samples. Platinisation of the samples with different nominal amounts of platinum (from 0.5 to 2.5 wt%) was performed and the influence of sulphate treatment on the dispersion and deposit size of platinum on the TiO2 surface was studied. Characterisation results and photocatalytic activity of these catalysts were compared with those of unmodified TiO2. Simultaneously sulphated and platinised TiO2 samples were highly active for phenol degradation, used as model reaction for the photocatalytic studies, having higher activities than only platinised or only sulphated samples. The activity of these samples were several orders of magnitude higher than that of the commercial TiO2 Degussa P25 (platinised or unmodified) as well, with independence of the nominal amount of platinum of the samples. A wide characterisation of the samples was performed and correlations between characterisation results and activity properties are reported. (C) 2007 Elsevier B.V. All rights reserved.