Chemistry Reference
In-Depth Information
Fig. 10.2 Sequential STM images of the assembly process of an H
2
O-(OH)
2
complex from
individual water molecules on a Cu(110) surface. a A water molecule and two oxygen atoms are
imaged as a round protrusion and two depressions, respectively. The white grid lines indicate the
lattice of Cu(110). The water molecule is dragged along the [110] direction toward atomic
oxygen (dashed arrow). b The reactants yield an (OH)
2
imaged as a semicircular depression. The
white dots indicate the nearest short-bridge sites to which oxygen atoms in (OH)
2
are bonded.
c Schematic illustration of the process of (a-b).(d-e) Subsequently, the other water molecule is
manipulated toward the end of (OH)
2
(dashed arrow), then yielding an H
2
O-(OH)
2
complex. The
three dots in (e) depict the nearest short-bridge sites to which oxygen atoms in the complex are
bonded. It is noted that the positions of oxygen atoms deviate slightly from the exact short-bridge
sites along [001] axis, as shown in the structure optimized by DFT calculations (Fig.
10.3
a and
b). f Schematic illustration of the process of (d-e). The images were recorded in constant current
mode at V
s
= 24 mV and I
t
= 0.5 nA. The image sizes are 20 9 58 Å
2
for (a and b), and
20 9 36 Å
2
for (d) and (e)
H
2
O-OH overlayer is exposed to H
2
O to recover the bare Pt area with water. The
time-evolution of the distribution of H
2
O and OH along the surface was observed
by the micro-XPS. From statistical analyses based on a diffusion equation, they
found two distinguishable proton transfer pathways with the diffusion coefficient
of *3.0 9 10
-12
and *9.9 9 10
-13
m
2
s
-1
, and dwell time of *5.2 and 48 ns
for the simple proton transfer from H
2
O to adjacent OH at 140 K.
