Cu-doped TiO2 systems with improved photocatalytic activity

Photocatalytic oxidation of phenol was performed over copper doped TiO2 prepared by a sol–gel method. Different preparation methods were followed and a comparison with undoped system was also made. Wide structural and surface characterization of catalysts was carried out in order to establish a correlation between the effect of sulphuric and nitric acids present in the initial solution and the Cu–TiO2 photocatalytic properties. The presence of sulphuric acid clearly stabilizes Cu–TiO2 and TiO2 structure and surface against sintering, maintaining anatase phase and relatively high surface area values with respect non sulphated Cu–TiO2 or TiO2. Best photocatalytic behaviour is found for sulphated TiO2, as previously reported. In addition, incorporation of copper ions into the structure seems to enhance the photoactivity of the system for acidified systems, being the sulphated one the most favourable photocatalyst. The optimum metal loading is found for 0.5 M% of copper ion. A possible explanation of this photocatalytic improvement might be related to the stabilization of Cu2O species in doped TiO2 prepared in the presence of sulphuric acid. This stabilization could be related to the presence of oxygen vacancies generated in the preparation procedure using sulphuric acid.