328
10 Electrochemical Manufacturing Methods Based on Surface …
properties. For the same reason, catalysts in fuel cells are often composed of a
carbon substrate partly coated with noble metal particles. Another typical substrate
is indium tin oxide (ITO) that is commonly used for depositing either metallic [3,
9–11] or semiconductor [12–14] nanoparticles. Whenever an optical study is aimed
at, the application of ITO is very convenient since it is transparent and has nearly
negligible interference with the light absorption or scattering properties of the particles studied. Metallic substrate, although they are less inert than either carbon-type
or ITO substrates, can be used if the deposit is less noble than the substrate [11, 14].
The concentration of the metal ions in the solution is mostly in the range of
0.05–10 mM (the more noble is the metal used, the concentration is usually the
smaller). The reason for the small metal ion concentration is that the probability
of the nucleation is proportional, among others, to the precursor ion concentration.
Therefore, the small precursor ion concentration leads to the nucleation of relatively
well-separated crystals that do not coalesce shortly after the nucleation event. The
deposition time may vary between a few seconds to about an hour, and obviously the
amount of the deposit is determined by the charge passed that leads to deposit formation. In the case when the deposition mode does not correspond to the pulse sequence
shown in Fig. 10.1, continuous potential cycling or square-wave voltammetry could
be used for the particle synthesis. All methods can be used for the synthesis of either
elemental or alloyed nanoparticles. For alloyed particles, the codeposition mode has
little influence on the composition of the particles when the deposition takes place
in the diffusion-controlled regime.
The shape control of the particles deposited is often crucial to achieve the desired
catalytic properties. While the substrate itself may have a crucial role in the determination of the particle shape [8], the deposition temperature has also a great influence [15], various additives can be used to achieved different particle shapes [11,
13, 14] and the shape of the particles can also be modified with post-deposition
electrochemical treatments [7].
10.3 Electrodeposition on Surfaces with Step Edges
10.3.1 General Considerations Concerning the Deposition
Along Step Edges
Step edge decoration was developed by physical deposition techniques on singlecrystal metal surfaces [16, 17]. The basic idea of this process is that adatoms tend
to accommodate at the step edge of the single-crystal surfaces, and growth may
start along the step edge as a deposited nanowire, especially at small deposition rate
of atoms with high surface mobility. Step edge-decorated samples obtained with
physical methods played an important role in studies of one-dimensional magnetism
with non-magnetic substrates and ferromagnetic nanowire deposits at the step edge.
When physical methods were applied for the sample preparation, the specimens
10 Electrochemical Manufacturing Methods Based on Surface …
properties. For the same reason, catalysts in fuel cells are often composed of a
carbon substrate partly coated with noble metal particles. Another typical substrate
is indium tin oxide (ITO) that is commonly used for depositing either metallic [3,
9–11] or semiconductor [12–14] nanoparticles. Whenever an optical study is aimed
at, the application of ITO is very convenient since it is transparent and has nearly
negligible interference with the light absorption or scattering properties of the particles studied. Metallic substrate, although they are less inert than either carbon-type
or ITO substrates, can be used if the deposit is less noble than the substrate [11, 14].
The concentration of the metal ions in the solution is mostly in the range of
0.05–10 mM (the more noble is the metal used, the concentration is usually the
smaller). The reason for the small metal ion concentration is that the probability
of the nucleation is proportional, among others, to the precursor ion concentration.
Therefore, the small precursor ion concentration leads to the nucleation of relatively
well-separated crystals that do not coalesce shortly after the nucleation event. The
deposition time may vary between a few seconds to about an hour, and obviously the
amount of the deposit is determined by the charge passed that leads to deposit formation. In the case when the deposition mode does not correspond to the pulse sequence
shown in Fig. 10.1, continuous potential cycling or square-wave voltammetry could
be used for the particle synthesis. All methods can be used for the synthesis of either
elemental or alloyed nanoparticles. For alloyed particles, the codeposition mode has
little influence on the composition of the particles when the deposition takes place
in the diffusion-controlled regime.
The shape control of the particles deposited is often crucial to achieve the desired
catalytic properties. While the substrate itself may have a crucial role in the determination of the particle shape [8], the deposition temperature has also a great influence [15], various additives can be used to achieved different particle shapes [11,
13, 14] and the shape of the particles can also be modified with post-deposition
electrochemical treatments [7].
10.3 Electrodeposition on Surfaces with Step Edges
10.3.1 General Considerations Concerning the Deposition
Along Step Edges
Step edge decoration was developed by physical deposition techniques on singlecrystal metal surfaces [16, 17]. The basic idea of this process is that adatoms tend
to accommodate at the step edge of the single-crystal surfaces, and growth may
start along the step edge as a deposited nanowire, especially at small deposition rate
of atoms with high surface mobility. Step edge-decorated samples obtained with
physical methods played an important role in studies of one-dimensional magnetism
with non-magnetic substrates and ferromagnetic nanowire deposits at the step edge.
When physical methods were applied for the sample preparation, the specimens