Scanning tunneling microscopy study of acrolein adsorbed on Cu(111)

Acrolein is the simplest α, β-unsaturated aldehyde, and its selective hydrogenation on metal surfaces is of fundamental interest. Here, we investigate the adsorption structures of acrolein molecules on Cu(111) by scanning tunneling microscopy. At low temperatures, chemisorbed and physisorbed monomers as well as dimers are observed. The thermally most stable chemisorbed monomer is assigned to twelve symmetry-equivalent adsorption orientations on Cu(111). The observed asymmetry between the C=C and C=O groups provides microscopic insight into the adsorption geometries relevant to selective hydrogenation.