86
[6]. Figure 7.4 shows a typical voltammetry curve with two peaks for the UPD of
Cu on a Rh(111) surface. The charge associated with these peaks is 540 μC/cm
2
,
which is close to 524 μC/cm
2
, needed for depositing a pseudomorphic monolayer of
Cu on an ideal Rh(111) surface. The most negative peak is very close to the bulk
deposition of Cu, which imposes careful control of the Cu UPD deposition to avoid
deposition of more than a monolayer of Cu. This is critical since the amount of
deposited Pt corresponds to the UPD Cu coverage. The dashed line shows the curve
for an Rh(111) surface in the absence of Cu ions in solution. Figure 7.4 also shows
the in situ scanning tunneling microscopy (STM) image of the Pt ML deposited using
a galvanic displacement of a Cu monolayer on a Rh(111) surface obtained at open
circuit potential in 0.1 M HClO 4 solution [7].
Fig. 7.3 Cells and setup
for Pt ML deposition by
displacement of Cu UPD
monolayer [6]
Fig. 7.4 Voltammetry curves for the underpotential deposition of Cu on a Rh(111) surface (solid
line) in 0.05 M H 2 SO 4 with 0.05 M Cu
2+ and for a Rh(111) surface in the absence of Cu
2+ (dashed
line); sweep rate 20 mV/s (left), and a in situ STM image of Pt ML on a Rh(111) surface obtained at
open circuit potential in 0.1 M HClO 4 solution. Image size is 47 × 47 nm, Z range 3 nm (right).
From [7] by permission of the American Chemical Society
7 Platinum Monolayer Electrocatalysts