Photoactivity of shape-controlled TiO2 in gas-solid regime under solar irradiation

Differently shape-controlled anatase TiO2 materials were tested as photocatalysts under both simulated and natural solar irradiation. Their photocatalytic activity in 2-propanol and propene partial oxidation and in the complete mineralization of acetaldehyde appears to increase with decreasing the shape control of the TiO2 material. This insight seems to be related to the residual presence of the templating species (fluoride anions) employed during the preparation of the shape-controlled TiO2 materials. In fact, the calcination of the powders, leading to levelling of the fluoride ions content, but also to a remarkable surface area decrease, gave rise to an increase of photocatalytic activity per unit surface area of the materials. In these photocatalytic materials two opposing effects may concur in determining their photoactivity, i.e. the possibly beneficial effect of an increased extent of exposed 001 facets and the detrimental effect resulting from a larger amount of residual fluoride ions employed as capping agents during their synthesis.