Density functional theory study of NO-H2O coadsorption on Cu(111)

The coadsorption and complex formation of nitric oxide (NO) and water (H2O) on Cu(111) are studied theoretically using the nonlocal van derWaals density functional method. The energetics, adsorption geometries, and vibrational properties of several nNO-mH(2)O complexes (n = 1-4, m = 1-3) on Cu(111) are reported, and the relative stabilities of those complexes are compared with their respective NO and H2O clusters on Cu(111). We find that the mixed nNO-mH(2)O complexes on Cu(111) are more stable than separated NO and H2O clusters due to the attractive NO-H2O and NO-NO interactions on the surface. The attractive NO-H2O interaction originates mainly from the hydrogen bonding between H2O and the negatively charged NO upon adsorption. Moreover, hydrogen bonding also induces an additional back donation process from Cu(111), further strengthening the NO-H2O coadsorption. In addition to hydrogen bonding, the NO-NO interaction originating from 2p * orbital hybridization further stabilizes the formation of the 4NO-3H(2)O complex, which is observed in the experiment. Even though the hydrogen bonding strength in NO-H2O complexes is slightly weaker than the one in H2O clusters, due to the saturation of hydrogen bonding and the NO-NO interaction, NO and H2O tends to form a mixed NO-H2O complex on Cu(111), in agreement with experiment. Our findings shed light on the role of intermolecular interactions between NO and H2O in the formation of the NO complex, which is important for understanding the reaction of NO in three-way catalysts.

Automated summary

This study investigates the coadsorption and complex formation of nitric oxide (NO) and water (H2O) on Cu(111) using theoretical methods. The results show that mixed nNO-mH(2)O complexes on Cu(111) are more stable than separated NO and H2O clusters due to attractive NO-H2O and NO-NO interactions. Hydrogen bonding and NO-NO interaction play crucial roles in the coadsorption.