Effect of surface chemistry and crystallographic parameters of tio₂ anatase nanocrystals on photocatalytic degradation of bisphenol A

The photocatalytic activity of a series of anatase TiO₂ materials with different amounts of exposed (001) facets (i.e., 12% (TiO₂-1), 38% (TiO₂-3), and 63% (TiO₂-3)) was tested in a batch slurry reactor towards liquid-phase bisphenol A (BPA, c₀ (BPA) = 10 mg/L, c_cat. = 125 mg/L) degradation. Photo-electrochemical and photo-luminescence measurements revealed that with the increasing amount of exposed anatase (001) facets, the catalysts generate more electron-hole pairs and OH· radicals that participate in the photocatalytic mineralization of pollutants dissolved in water. In the initial stages of BPA degradation, a correlation between % exposure of (001) facets and catalytic activity was developed, which was in good agreement with the findings of the photo-electrochemical and photo-luminescence measurements. TiO₂-1 and TiO₂-3 solids achieved 100% BPA removal after 80 min in comparison to the TiO₂-2 sample. Adsorption of BPA degradation products onto the TiO₂-2 catalyst surface was found to have a detrimental effect on the photocatalytic performance in the last stage of the reaction course. Consequently, the global extent of BPA mineralization decreased with the increasing exposure of anatase (001) facets. The major contribution to the enhanced reactivity of TiO₂ anatase (001) surface is the Brønsted acidity resulting from dissociative chemisorption of water on a surface as indicated by FTIR, TPD, and MAS NMR analyses.