Ultrathin (001) and (100) TiO2(B) sheets: Surface reactivity and structural properties

Abstract B polymorph of titanium dioxide (TiO 2 (B)) appears as a metastable phase during thermal annealing of low content sodium layered titanate nanostructures obtained via the widely used hydrothermal synthesis. In addition, the computed formation energy for the TiO 2 (B) (0 0 1) slabs in the order of the one calculated for anatase (1 0 1) which represents one of the most stable TiO 2 surfaces. This encourages the study of this polymorph which could gain prominence in TiO 2 applications at the nanoscale. In a first instance ultrathin TiO 2 (B) sheets, parallel to crystallographic planes (0 0 1) and (1 0 0), are investigated and compared to other well know TiO 2 polymorphs, such as rutile and anatase surfaces. Then the adsorption of formic acid on (0 0 1) and (1 0 0) – less stable – TiO 2 (B) dry ultrathin sheets was studied as the first step for further evaluation of TiO 2 (B) nanostructures for dye sensitized solar cells (DSSC) applications. The results show that the monodentate through the carbonyl group configuration is the most stable for (0 0 1) sheet while bidentate dissociated configuration is the most stable for (1 0 0) sheet being the computed adsorption energies 0.51 eV and 1.49 eV, respectively. The evaluated reactivity of TiO 2 (B) slabs is comparable with anatase and indicates that it could be a good adsorbent for common dyes used for dye sensitized solar cells purposes.