Oxygen chemisorption-induced surface phase transitions on Cu(110)

a r t i c l e i n f o From an interplay between variable temperature scanning tunneling microscopy and density–functional theory calculations, the evolution of oxygen chemisorption-induced surface reconstructions of the Cu(110) surface is determined. The surface reconstructions proceed via a sequential pathway with increasing oxygen surface coverage. The (2 × 1) reconstruction occurs first and then transits to the c(6 × 2) phase with a higher oxygen coverage through a mechanism that consumes the existing (2 × 1) phase with the supply of Cu adatoms from step edges and terraces. The temperature dependence of the (2 × 1) → c(6 × 2) transition demonstrates that the surface phase transition is an activated process for breaking up added Cu–O–Cu rows in the (2 × 1) structure. Comparison between the experimental observations and the theoretical surface phase diagram obtained from first-principles thermodynamic calculations reveals that the (2 × 1) → c(6 × 2) transition takes place at the oxygen chemical potentials that are far above the chemical potential for Cu 2 O bulk oxide formation, reflecting the existence of kinetic limitations to the surface phase transition and the bulk oxide formation. Effects resulting from the interaction between oxygen and a metal surface are of great interest in many areas such as oxidation, corrosion, and heterogeneous catalysis. Acquiring a fundamental understanding of the nature of the interactions is critical to elucidate the role of oxygen for these important technological processes. For instance, many current industrial processes are centered on catalytic oxidation reactions. Upon exposure to an oxygen-containing atmosphere, the metal surface undergoes a series of structural changes varying from the formation of initial oxygen chemisorbed adlayers to oxygen sub-surface diffusion and then to bulk oxide formation, depending on the oxidation conditions including the oxygen gas partial pressure, temperature, and orientation of the metal surface. It has been increasingly apparent that the active phase of some catalytic oxidation catalysts under operating conditions is in fact their oxides rather than the pure metal [1,2]. During catalytic reactions different compositions and structures of the metal surface may be present depending on the operation conditions. However , not all oxide phases are equally active to fulfill multiple catalytic functions. Thus, a detailed study of the formation of each surface reconstruction and the mechanism governing their transitions to other phases will provide insight for finely tuning the operating conditions to favor one phase over the …