Hydroxyl radical and free and shallowly trapped electron generation and electron/hole recombination rates in TiO2 photocatalysis using different combinations of anatase and rutile

Hydroxyl radical (OH center dot) and electron (e(-) ) generation in aqueous suspensions during TiO2 photocatalysis was studied, varying the properties of the photocatalyst and using the molecular probes terephthalic acid (TA) for OH center dot and resazurin dye (Rz) for electrons. Overall photocatalytic activity was calculated from rhodamine B dye degradation. The percentage of e(-) recombination was found as the difference between the results for aqueous Rz in the presence and absence of a hole scavenger (glycerol). The findings show that the properties of the TiO2 particles affect e(-) and OH center dot generation rates differently. The generation rates of these active species and their overall photocatalytic activity were observed to be heavily dependent upon the physical properties of the TiO2 used and the recombination percentage.