Reduction and fragmentation of CS2 at the surface of electron-rich MgO: an EPR study

Abstract

Sulfur contamination of alkaline earth oxide surfaces has important consequences in many fields of chemistry, such as surface science and catalysis. We used the Electron Paramagnetic Resonance (EPR) technique to study the interaction of CS2 molecules under different pressure and temperature conditions, with the bare and electron-enriched surface of MgO. CS2 reacts on the oxide surface through two distinct reaction paths, one leading to diamagnetic species, the other to paramagnetic surface entities. Both these reaction paths lead to the fragmentation of the CS2 molecule and, in some cases to oligomerization processes. EPR experiments allowed to follow the formation of the unstable CS 2 − radical intermediate and its evolution through formation of several surface radicals like S−, S 3 − and S n − (n ⩾ 3), depending on the reaction conditions.