Density Functional Theory Study of Monoethanolamine Adsorption on Hydroxylated Cr2O3 Surfaces

The adsorption of monoethanolamine (MEA), a well-known CO2 capture amine, on the hydroxylated (0001)-Cr2O3 surface was investigated by periodic density functional theory calculations and complementary ab initio molecular dynamics. Two different adsorption modes were investigated: adsorption of MEA above the hydroxylated surface and substitution of a surface water molecule by MEA. Several MEA coverages were studied from 0.25 to 1 monolayer. An atomistic thermodynamic approach was used to take into account the effects of temperature and solvation on the MEA adsorption process in aqueous solution. MEA can adsorb on the surface in a parallel orientation, and H-bonds are formed between amine and alcohol groups and different (H)OH groups at the surface. In the gas phase at 0 K, the formation of a monolayer (ML) of MEA above the surface is the most favorable adsorption mode. In aqueous solution at 298.15K, calculations have suggested that MEA adsorbs above the hydroxylated Cr2O3 surface with a density of 2.37 MEA/nm(2) (0.5 ML). However, the substitution process was found to be endothermic at temperatures above 298.15 K.