Reaction kinetics and mechanism of oxygen adsorption on the Ni(1 1 0) surface

The reaction scheme of O2 with a Ni(1 1 0) surface is investigated from 133 to 703 K by low energy electron diffraction (LEED) and kinetic study. The phase diagram of the O/Ni(1 1 0) surface is presented by means of the LEED pattern variation as a function of the O2 exposure in isothermal conditions. The adsorption kinetics of O2 was quantitatively measured using a differentially pumped line of sight quadrupole mass spectrometer. When Ni(1 1 0) clean surface is exposed to the O2 below 340 K, disordered NiO is formed. For exposure between 340 and 470 K, the surface reconstructs into the sequence of the (2×1) 1/2 and the (3×1) 2/3 ML missing-row structures, and thereafter a (9×5) suboxide structure develops followed by the growth of an epitaxial NiO(0 0 1) layer on top of the metal substrate. Between 470 and 570 K, after the formation of the (3×1) missing-row structure, extra O atoms penetrate into the Ni sublayer leaving the (3×1) structure on the surface, and finally a weak complicated LEED pattern is observed with NiO formation. Above 570 K, the excess surface O and extra chemisorbed O atoms dissolve into the bulk leaving the (2×1) structure on the surface.