Adsorption and dissociation of Ammonia on the hydroxylated surface of magnesium oxide powders

Abstract

A systematic infrared study has been performed concerning ammonia adsorption on high-surface-area MgO at successive stages of surface dehydroxylation. Ammonia is mostly held in molecular forms by hydroxyls, Mg²⁺ cations and O^2– anions exposed in low coordination on {001} planes. Heterolytic dissociation is also observed not only on fully dehydroxylated but also on hydroxylated samples. This process is monitored by the NH^–₂ absorption at 1555 cm^–1.