Surface and Bulk Distribution of Fluorides and Ti3+ Species in TiO2 Nanosheets: Implications on Charge Carriers Dynamics and Photocatalysis

The effect on the reactivity and the kinetic of photogenerated e-- h+ pairs induced by post-synthesis treatments on shape controlled TiO2 anatase nanosheets with dominant {001} facets are reported. Anatase nanosheets were prepared under hydrothermal conditions in the presence of fluoride ions as shape controllers. Fluorides were removed from the surface by washing with NaOH 0.1 M or by thermal treatment at 873 K. The effect of the progressive removal of fluorides on the electronic properties of the samples was monitored by EPR and UV-Vis-NIR-MIR spectroscopies, clearly separating the contributions of surface and bulk Ti3+ sites. The charge carrier dynamic was studied by EPR and photoelectrochemical measurements. These two complementary techniques provide insight into the recombination kinetics of the photogenerated carriers highlighting the role of both surface chemistry (F- vs OH- coverage) and morphology. The results indicate that the photocatalytic activity of TiO2 anatase nanosheets could be controlle...