Effects of anatase TiO2 morphology and surface fluorination on environmentally relevant photocatalytic reduction and oxidation reactions

Aiming at clarifying the interplay on TiO₂ photoactivity between particle morphology and surface fluorination, the photocatalytic performance of anatase nanocrystals, characterized by a pseudo-spherical shape or a nanosheet structure, is investigated in both a reduction and an oxidation reaction, either in the absence or in the presence of added fluoride anions. Cr(VI) photocatalytic reduction is strongly favored by a large exposure of anatase {001} facets; however, surface fluorination leads in this case to a morphology-independent photoactivity decrease, due to the decreased adsorption of the reaction substrate. More interestingly, a beneficial synergistic effect between the platelet-like anatase morphology and TiO₂ surface fluorination is clearly outlined in Rhodamine B photocatalytic degradation, possibly resulting from the intrinsic ability of fluorinated {001} anatase facets of boosting ^?OH radical mediated oxidation paths, due to their larger amount of surface –OH groups, as revealed using Fourier-transform infrared spectroscopy.