Preparation, Characterisation, and Photocatalytic Behaviour of Co‐TiO2 with Visible Light Response

Abstract

The preparation of cobalt‐modified TiO2 (Co‐TiO2) was carried out by the incipient impregnation method starting from commercial TiO2 (Degussa, P‐25) and cobalt acetate. XPS data show that cobalt is incorporated as divalent ion, and it is likely present within few subsurface layers. No appreciable change in structural‐morphologic properties, such as surface area and anatase/rutile phase ratio, was observed. Conversely, Co addition brings about conspicuous changes in the point of zero charge and in surface polarity. Diffuse reflectance spectra feature a red shift in light absorption that is dependent on the amount of cobalt. The influence of cobalt addition on the performance of TiO2 as a photocatalyst in the degradation of 4‐chlorophenol and Bisphenol A is investigated. The results show that the modified oxide presents a higher photoactivity both for illumination with UV‐visible (λ > 360 nm) and visible light (λ > 420 nm; λ > 450 nm), and that this enhancement depends on the amount of the added species and on the final thermal treatment in the preparation step. We also show that Co‐TiO2 is a more active catalyst than pure TiO2 for the reduction of O2 in the dark, which is an important reaction in the overall photocatalytic processes.