TY - JOUR

T1 - The effect of coadsorbed oxygen on the adsorption and diffusion of potassium on Rh(110)

T2 - A first-principles study

AU - Xu, Ye

AU - Marbach, Hubertus

AU - Imbihl, Ronald

AU - Kevrekidis, Ioannis G.

AU - Mavrikakis, Manos

PY - 2007/5/1

Y1 - 2007/5/1

N2 - The adsorption and diffusion of potassium and oxygen on Rh(110), as well as the coadsorption of K and O and its effect on K diffusion, have been studied using periodic density functional theory (DFT) calculations (PW91-GGA). On both the nonreconstructed (1 × 1) and the missing-row (MR) reconstructed surfaces, O prefers the short bridge site at low coverage, with a binding energy of ca. -5.2 eV at 1/4 ML. At θo > 1/2 ML, O atoms occupy alternating threefold sites along the ridge and form a zigzag pattern. Interaction with the ridge sites is enhanced by the MR reconstruction. Potassium prefers to be in the trough, with a binding energy of -2.3 eV on the (1 × 1) surface and -2.9 eV on the MR surface at 1/8 ML. Thus, the adsorption of both O and K at low to medium coverage promotes the MR reconstruction. The coadsorption of K and O enhances the binding energy of K to a maximum of -3.6 eV at the highest oxygen coverage studied, 13/8 ML. Oxygen adsorption is also stabilized by K, though to a smaller extent on a per-O-atom basis. On both surfaces, K prefers to diffuse in the [11̄0] direction with a barrier of ca. 0.05 eV. Oxygen diffusion also prefers the [11̄0] direction on the MR surface but is not clearly anisotropic on the (1 × 1) surface. The barrier to O diffusion ranges from 0.6-0.8 eV depending on the coverage and reconstruction. In the presence of coadsorbed O, the diffusion barrier of K tops out at ca. 0.12 eV, much lower than earlier estimates based on mean-field models. Possible reasons for this apparent contradiction are discussed.

AB - The adsorption and diffusion of potassium and oxygen on Rh(110), as well as the coadsorption of K and O and its effect on K diffusion, have been studied using periodic density functional theory (DFT) calculations (PW91-GGA). On both the nonreconstructed (1 × 1) and the missing-row (MR) reconstructed surfaces, O prefers the short bridge site at low coverage, with a binding energy of ca. -5.2 eV at 1/4 ML. At θo > 1/2 ML, O atoms occupy alternating threefold sites along the ridge and form a zigzag pattern. Interaction with the ridge sites is enhanced by the MR reconstruction. Potassium prefers to be in the trough, with a binding energy of -2.3 eV on the (1 × 1) surface and -2.9 eV on the MR surface at 1/8 ML. Thus, the adsorption of both O and K at low to medium coverage promotes the MR reconstruction. The coadsorption of K and O enhances the binding energy of K to a maximum of -3.6 eV at the highest oxygen coverage studied, 13/8 ML. Oxygen adsorption is also stabilized by K, though to a smaller extent on a per-O-atom basis. On both surfaces, K prefers to diffuse in the [11̄0] direction with a barrier of ca. 0.05 eV. Oxygen diffusion also prefers the [11̄0] direction on the MR surface but is not clearly anisotropic on the (1 × 1) surface. The barrier to O diffusion ranges from 0.6-0.8 eV depending on the coverage and reconstruction. In the presence of coadsorbed O, the diffusion barrier of K tops out at ca. 0.12 eV, much lower than earlier estimates based on mean-field models. Possible reasons for this apparent contradiction are discussed.

UR - http://www.scopus.com/inward/record.url?scp=34250316552&partnerID=8YFLogxK

U2 - 10.1021/jp070654v

DO - 10.1021/jp070654v

M3 - Article

AN - SCOPUS:34250316552

VL - 111

SP - 7446

EP - 7455

JO - Journal of Physical Chemistry C

JF - Journal of Physical Chemistry C

SN - 1932-7447

IS - 20

ER -