Formate Adsorption on Cu(110), Ag(110) and Au(110) Surfaces

The adsorption of formate (HCOO) on Cu(110), Ag(110), and Au(110) surfaces has been studied by the density functional theory (DFT) and generalized gradient approximation (GGA) with slab model. To find the most stable adsorption site of HCOO on M(110) (M=Cu, Ag, Au), we investigated several adsorption forms like bidentate and monodentate adsorption sites. The calculated results show that the most stable adsorption site is short-bridge bidentate form for all the three metals, which is independence of the metallic lattice constants. The calculated atomic geometries agree well with the experimental results and the previous calculation results. Adsorption energy of formate follows the order of Cu(110) (-116 kJ . mol(-1))>Ag(110)(-57 kJ . mol(-1))>Au(110)(-27 kJ . mol(-1)), in agreement with decomposition temperature of formate measured by experiments. The order of the adsorption energy can be explained by Pauli repulsion between molecular orbitals of formate with d-band of metal, i.e., the more occupied population of formate. the larger Pauli repulsion, which results in the weaker adsorption of formate. In addition, the activation energy of formate synthesis from CO2 and H-2 was predicated using the adsorption energy of formate and the decomposition temperature of formate, which follows the order of Au(110)>Ag(110)>Cu(110).