A low-energy electron diffraction study of potassium - oxygen coadsorption phases on Ni(111)

Abstract

The coadsorption of potassium and oxygen on a Ni(111) surface has been studied by low-energy electron diffraction (LEED). The initial potassium-induced structures on the bare and the oxygen-monolayer-covered surface exhibit similar LEED ring patterns, which may be attributed to the strong dipole - dipole repulsive interaction in both cases. On the other hand, a small amount of pre-adsorbed oxygen (θ0<0.1) prevents the formation of the potassium ring phase, suggesting an attractive K - O interaction. Once all of the pre-adsorbed oxygen is attached to the potassium adatoms, further potassium adsorption produces the same phases as on the oxygen-free surface. For intermediate O precoverages, a gradual structural transformation from a p(2 × 2) to a phase is observed upon K adsorption. Potassium reduces the critical oxygen coverage for the completion of this phase transformation, suggesting that (disordered) K mixes in the O layer. At higher O precoverages, coadsorption results in a new c(4 × 2) ordered phase in a structure which probably involves both K and O.

Comparative vibrational study on alkali coadsorption with CO and O on Ni(111) and Cu(111)

“…The adsorption of alkali-metal atoms on single-crystal metal surfaces [1][2][3][4][5][6][7][8] and their coadsorption [9][10][11][12][13][14] with reactive species are a topic of surface science, both of fundamental interest in understanding the mechanisms of heterogeneous catalysis and for technological applications (promotion of catalytic reactions, oxidation rate and enhanced electron emission rates).…”

“…However, an increased K-Ni bond length was revealed. In the case of K + O, a complete low-energy electron diffraction (LEED) investigation has been performed by Li and Diehl [40].…”