Adsorption of CO on the Ca₃Ru₂O₇(001) surface

Abstract

The adsorption of CO molecules at the Ca3Ru2O7(001) surface was studied using low-temperature scanning tunneling microscopy (STM) and density functional theory (DFT). Ca3Ru2O7 can be easily cleaved along the (001) plane, yielding a smooth, CaO-terminated surface. The STM shows a characteristic pattern with alternating dark and bright stripes, resulting from the tilting of the RuO6 octahedra. At 78 K, CO adsorbs at an apical surface O at the channel edge with a predicted binding energy of Eads = −0.85 eV. After annealing at room temperature, the CO forms a strong bond (Eads = −2.04 eV) with the apical O and the resulting carboxylate takes the place of the former surface O. This carboxylate can be decomposed by scanning the surface with a high sample bias voltage of +2.7 V, restoring the original surface.