Trends
in the Adsorption and Dissociation of Water
Clusters on Flat and Stepped Metallic Surfaces
- Publication date
- Publisher
Abstract
Understanding the structure and chemical
reactivity of water adsorbed
at metallic surfaces is very important in many processes such as catalysis,
corrosion, and electrochemistry. Using density functional theory calculations,
we investigate the adsorption and dissociation of water clusters on
flat and stepped surfaces of several transition metals: Rh, Ir, Pd,
and Pt. We find that water binds preferentially to the step edges
than to terrace sites, thus linear clusters or one-dimensional water
wires can be isolated by differential desorption. The clusters formed
at the step are stabilized by the cooperative effect of chemical bonds
with the metal and hydrogen bonding. The enhanced reactivity of the
step edges and the cooperative effect of hydrogen bonding improve
the chances of partial dissociation of water clusters. We assess the
correlations between adsorption and dissociation energies, observing
that they are increased on stepped surfaces. We present a detailed
interpretation of water dissociation by analyzing changes in the electronic
structure of both water and metals. The identification of trends in
the energetics of water dissociation at transition metals is expected
to aid the design of better materials for catalysis and fuel cells,
where the density of steps at surfaces would be a relevant additional
parameter