Influence of crystallinity and OH surface density on the photocatalytic activity of TiO2 powders

The aim of the work was to study the influence of crystallinity and OH surface density on the photocatalytic activity of two commercial and two home-prepared TiO2 powders. The samples were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TG) and electron paramagnetic resonance (EPR) measurements. The photoactivity of the powders was tested employing the photodegradation of 4-nitrophenol (4-NP) and the selective oxidation of 4-methoxybenzyl alcohol (4-MBA) to 4-methoxybenzaldehyde (p-anisaldehyde) under UV irradiation. An anti-correlation between oxidant power and selectivity of the various samples was found. A higher rate of 4-NP degradation was exhibited by the most crystalline commercial samples, whereas the highest selectivity toward the synthesis of p-anisaldehyde was obtained in the presence of the least crystalline and most hydroxylated home-prepared powders.