IR study of CS 2 adsorption on metal oxides: relation with their surface oxygen basicity and mobility

Abstract

Adsorption of CS 2 on a series of metal oxides (Al 2O 3, ZrO 2, ZnO and CeO 2) activated at 723 or 973 K was studied at room temperature by FT-IR spectroscopy. In addition to hydrogen thiocarbonate and carbonate species, a new species, characterized by bands in the 1200–1000 cm −1 range, was evidenced. Its amount increased by increasing activation temperature of metal oxides. Co-adsorption experiments of CS 2 with either CO 2 or pyridine showed that its adsorption sites are mainly those giving rise to bidentate carbonates from CO 2. Experiments on ZrO 2 preechanged by H 2 18O confirmed CS 2 adsorption on basic O 2− sites. Xanthate (COS 2) 2− species formation was proposed. Results were compared with metal oxide basicity and a nice agreement was observed. However, on ceria, carbonates formation easily occurred from CS 2 adsorption, even at room temperature, suggesting that CS 2 can probe both surface basicity, through the intensity of bands due to xanthate species, and surface oxygen mobility, involved in the surface transformation of xanthate into carbonate species.