Two probe photocatalytic reactions, i.e. ethanoic acid and 4-nitrophenol photooxidation, were
carried out in different experimental conditions by using suspensions of transition metal (Co, Cr, Cu, Fe,
Mo, V and W) doped polycrystalline TiO2 powders in aqueous systems. A beneficial influence of the presence
of metal species was observed only with the samples containing copper and tungsten. In particular,
the TiO2/Cu powders showed to be more photoactive of bare TiO2 for the ethanoic acid oxidation while the
TiO2/W samples were more efficient for 4-nitrophenol degradation. A tentative interpretation is provided
on the basis of the values of the points of zero charge of the powders and of the rate constants of recombination
of photogenerated electrons and holes, determined by femtosecond pump-probe diffuse reflectance
spectroscopy (PP-DRS).
