Reaction kinetics and mechanism of oxygen adsorption on the Ni(110) surface

The reaction scheme of O-2 with a Ni(1 1 0) surface is investigated from 13 3 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 O-2 exposure in isothermal conditio ns. The adsorption kinetics Of O-2 was quantitatively measured using a diff erentially pumped line of sight quadrupole mass spectrometer. When Ni(1 1 0 ) clean surface is exposed to the O-2 below 340 K, disordered NiO is formed . For exposure between 340 and 470 K, the surface reconstructs into the seq uence of the (2 x 1) 1/2 and the (3 x 1) 2/3 ML missing-row structures, and thereafter a (9 x 5) suboxide structure develops followed by the growth of an epitaxial NiO(0 0 1) layer on top of the metal substrate. Between 470 a nd 570 K, after the formation of the (3 x 1) missing-row structure, extra O atoms penetrate into the Ni sublayer leaving the (3 x 1) structure on the surface, and finally a weak complicated LEED pattern is observed with NiO f ormation. Above 570 K, the excess surface O and extra chemisorbed O atoms d issolve into the bulk leaving the (2 x 1) structure on the surface. (C) 200 1 Elsevier Science B.V. All rights reserved.