Adsorption of CS2 on MgO microcrystals: formation of a S-doped MgO surface

Abstract

The interaction of carbon disulfide, CS₂, with polycrystalline MgO was investigated by means of infrared and UV–visible spectroscopies and ab initio electronic structure calculations. The aim was to understand the modifications of the surface properties of MgO microcrystals induced by the substitution of O²⁻ with S²⁻ anions. The interaction of CS₂ with MgO shows the formation of thiocarbonates followed by O–S exchange reactions and formation of Mg²⁺–S²⁻ clusters in a MgO matrix. The O–S exchange reaction involves mainly the low-coordinated O²⁻ anions at the steps and corner sites, and only at high temperature are a small number of O²⁻ anions at the (100) terrace sites involved. The replacement of the O with the S atoms at the low-coordinated sites of the MgO surface transforms the reactive polycrystalline material into a chemically inert system.