Origin of the Optimization of Photocatalytic Activities for Titanium Oxide Film Modified by an Oxidized Copper Layer.

In this study, the surface photocatalytic activity of an anatase-titanium oxide (TiO) film was modified by a thin copper (Cu) layer with the subsequential oxidation annealing process. Through this simple annealing process, the photocatalytic activity of the TiO/Cu structure to decompose the methylene blue solution and inhibit the growth of . could be optimized. With the help of a study on the conductive type required for the oxidation of a single Cu layer, an nanocomposite heterojunction was realized, as this contact system anneals at temperatures of 350 °C and 450 °C. An extra electrical field at the contact interfaces that was be beneficial for separating the photo-generated electron-hole pairs (EHPs) under UV light irradiation was built. The built-in electrical field led to an increase in the structural photocatalytic activity. Moreover, as the -type cuprous oxide (-CuO) structure oxidized by the annealed Cu layer could provide a high conduction band that is offset when in contact with the TiO film, the photogenerated EHPs on the TiO surface could be separated more effectively. Accordingly, the 350 °C-annealed sample, abundant in the nanocomposite TiO/CuO heterojunction which could significantly retard the recombination of photo-generated carriers, corresponded to an increase of about 38% in the photocatalytic activity as compared with the single TiO film.