Chemistry Reference
In-Depth Information
and higher coverage [
26
-
32
]. The water dissociation and hydroxyl formation on
Cu(110) were investigated mainly by means of the x-ray photoemission spec-
troscopy. The dissociation is only partial and water molecules survive against
desorption even at 428 K under a near-ambient pressure. It was proposed that
water molecules are anchored to OH groups and stabilized against desorption due
to a strong H
2
O-OH interaction. The STM revealed that the water-hydroxyl chain
complex grows along [110] after annealing the water-covered surface
to * 200 K. Since the water molecule is strongly bound in the bridge complex
found in the present work (E
b
= 0.78 eV), it may be a good candidate as a basis
that composes the thermal products observed previously.
9.3 Summary
The hydration reaction between water and hydroxyl was controlled at the single
molecule level using STM. Two distinct water-hydroxyl complexes were produced
selectively and they can be controlled by the initial geometry of the reactants
before the reaction. The structure and H-bonding nature in the complexes were
investigated by the comprehensive DFT calculations. Upon the reaction between
the two reactants on the same atomic row of Cu(110), the side-on complex was
formed, which was identified by a relatively weak H bond (0.13 eV). On the other
hand, upon the reaction between two reactants located on the adjacent rows, the
bridge complex was formed, which was characterized by the strong H bond
(0.44 eV) and the small distance between the two O atoms. Based on the detailed
analysis of the STM appearance and adiabatic and static potential calculations, it is
proposed that ''a low-barrier H bond'' is formed in the latter complex as a result of
the significant reduction of effective barrier for the proton transfer and the ZPE
within the H bond.
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