FTIR Spectroscopic and Density Functional Model Cluster Studies of Methane Adsorption on MgO

Methane adsorption on the MgO surface has been studied by combining FTIR spectroscopy and density functional (DF) cluster model calculations. Different configurations for the adsorbed methane molecule have been computationally investigated on both Lewis acid and basic surface centers located at the (100) planar surface and at the low-coordinated surface sites (edge and corner). Methane has been found to be very weakly bound on the MgO surface and mainly at the low-coordinated ions. Upon interaction with the surface, the C−H symmetric stretching mode (IR symmetry forbidden for the free molecule) becomes IR active and shifts toward lower frequencies. To account for the role of Lewis acid sites in methane adsorption, CO coadsorption has been also considered.