Transition metal doped TiO₂: physical properties and photocatalytic behaviour

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 TiO 2 /Cu powders showed to be more photoactive of bare TiO 2 for the ethanoic acid oxidation while the TiO 2 /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).