Gu. Kulkarni et al., COADSORPTION OF DIOXYGEN AND WATER ON THE NI(110) SURFACE - ROLE OF O--TYPE SPECIES IN THE DISSOCIATION OF WATER, Langmuir, 11(7), 1995, pp. 2572-2575
While the adsorption of dioxygen at a clean Ni(110) surface gives rise
to two O(1s) features at 531 and 530 eV assigned to O-(a) and O2-(a)
type species respectively, coadsorption of dioxygen and water mixtures
result in the additional formation of hydroxyl species characterized
by an O(1s) peak at 532.3 eV. The latter is attributed to the oxygen i
nduced dissociation of water via a low energy pathway involving the O-
(a)-type species. The proportions of the O-(a) and the hydroxyl specie
s are greater for small O-2/H2O ratios and lower temperatures (120 K).
With increase in temperature, the relative surface concentrations of
the O-(a) and the hydroxyl species decrease while there is an increase
in the concentration of the oxidic O2-(a) species. Thus, the surface
concentrations of both the hydroxyl and the O2-(a) species depend crit
ically on the presence of O- type species. Above 300K the surface chem
istry in the main involves the conversion of O- to O2- species via the
hydroxyl species.