Triethylamine (TEA) and NH 4 F-modified TiO 2 powders and thin films were prepared by combining solgel and hydrothermal processes. Modification with TEA results in increased specific surface area and induces energy states below the conduction band of TiO 2 . On the other hand, the use of NH 4 F decreases the band-gap, displacing the valence band. Employing radical-scavenging agents, it was found that formation of O 2 * is preferred in TEA-modified TiO 2 , whereas generation of both O 2 * and OH * results from simultaneous modification. Furthermore, the photocatalytic degradation rate was directly proportional to their specific surface area. However, this trend was reversed in a photoelectrocatalytic cell, due to the fact that the photogenerated electrons are rapidly transported to the rear contact, which restrains their transfer to the dissolved oxygen to generate O 2 * . Therefore, the presence of OH * radicals and direct charge transfer processes appears to play a key role in the photoelectrocatalytic process.
Graphical Abstract