Division of Environmental Physics - User: veronika
Faculty of Mathematics, Physics and Informatics, Comenius University Bratislava

Ce surface-modified TiO₂ aerogel powder: A comprehensive study of their excellent photocatalytic efficiency in organic pollutant removal

Thirunavukkarasu G., Monfort O., Motola M., Motlochová M., Gregor M., Roch T., Čaplovicová M., Lavrikova A. Y., Hensel K., Brezová V., Jerigová M., Šubrt J., Plesch G.
New J. Chem. 45 (9), 4174-4184 (2021)

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Abstract:

Titanium dioxide aerogel (TiAP) powders were prepared by lyophilization of peroxo-polytitanic gels followed by annealing at 800 °C to obtain anatase structure. The surface modification of TiAP was performed for the first time by low extents of Ce ions (in the range from 0.0025 to 0.025 wt%) using a wet impregnation method. Photocatalytic activity of the aerogel samples was investigated in the removal of different organic pollutants (i.e., Rhodamine B, phenol and caffeine) and compared to the reference P25. Both TiAP and Ce ions surface-modified TiAP (Ce/TiAP) have exhibited better degradation efficiencies of pollutants than P25, especially for Ce/TiAP with an enhancement of +18 % and +37 % in the removal of caffeine and Rhodamine B, respectively. These results have been partly explained by the high active surface area of Ce/TiAP compared to TiAP as well as its better photo-electrochemical properties which have shown, for instance, ~10 % increased incident photon-to-electron conversion efficiency at 360 nm. Interestingly, the energetic position of the valence band maximum of Ce/TiAP is shifted from 3.2 eV to 2.8 eV (compared to TiAP), thus improving the generation of reactive oxygen species (ROS), especially hydroxyl radicals. Indeed, the presence of HO• is confirmed by electron paramagnetic resonance, and fluorescence spectroscopy and their photo-induced generation are enhanced in the case of Ce/TiAP. Finally, the surface modification of TiAP by cerium ions led to better photo-induced properties, thus limiting the electronhole pair recombination, but also to the improvement of ROS generation via different plausible mechanisms.