Directing photocatalytic and photoelectrocatalytic performance of TiO₂ by using TEA and NH₄F as doping precursors

Abstract: Triethylamine (TEA) and NH₄F-modified TiO₂ powders and thin films were prepared by combining sol–gel and hydrothermal processes. Modification with TEA results in increased specific surface area and induces energy states below the conduction band of TiO₂. On the other hand, the use of NH₄F decreases the band-gap, displacing the valence band. Employing radical-scavenging agents, it was found that formation of O₂ ^* is preferred in TEA-modified TiO₂, whereas generation of both O₂ ^* 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 O₂ ^*. Therefore, the presence of OH^* radicals and direct charge transfer processes appears to play a key role in the photoelectrocatalytic process. Graphical Abstract: [Figure not available: see fulltext.]