Periodic density functional study of superacidity of sulfated zirconia

Abstract Periodic density functional theory (DFT) study was performed in order to investigate structural properties as well as electronic states of the sulfated zirconia (S-ZrO 2 ) surface. It was found that H 2 SO 4 dissociatively adsorbs on the tetragonal (1 0 1) ZrO 2 (t-ZrO 2 ) surface affording H 2 O and SO 3 molecules. The NH 3 adsorption analysis was also performed in order to evaluate the acid strength of both Bronsted and Lewis acid sites on the ZrO 2 surface. In the case of Bronsted acid sites, the proton on H 2 O and SO 3 co-adsorbed t-ZrO 2 surface shows stronger acidity than that of H 2 O solely adsorbed t-ZrO 2 surface. On the H 2 O and SO 3 co-adsorbed tetragonal surface, electron transfer from H 2 O molecule into ZrO 2 surface accompanied by that from ZrO 2 surface into SO 3 molecule, was observed. The analysis of Lewis acidity indicated that coordinatively unsaturated surface Zr atom which interacted with SO 3 molecule showed strong Lewis acidity.